Academic literature on the topic 'Connexin 37'

Vascular endothelial cells interact with one another via gap junctions, but information on the precise connexin make-up of endothelial gap junctions in intact arterial tissue is limited. One factor contributing to this lack of information is that standard immunocytochemical methodologies applied to arterial sections do not readily permit unequivocal localization of connexin immunolabeling to endothelium. Here we introduce a method for multiple labeling with specific endothelial cell markers and one or more connexin-specific antibodies which overcomes this limitation. Applying this method to localize connexins 43, 40, and 37 by confocal microscopy, we show that the three connexin types have quite distinctive labeling patterns in different vessels. Whereas endothelial cells of rat aorta and coronary artery characteristically show extensive, prominent connexin40, and heterogeneous scattered connexin37, the former, unlike the latter, also has abundant connexin43. The relative lack of connexin43 in coronary artery endothelium was confirmed in both rat and human using three alternative antibodies. In the aorta, connexins43 and 40 commonly co-localize to the same junctional plaque. Even within a given type of endothelium, zonal variation in connexin expression was apparent. In rat endocardium, a zone just below the mitral valve region is marked by expression of greater quantities of connexin43 than surrounding areas. These results are consistent with the idea that differential expression of connexins may contribute to modulation of endothelial gap junction function in different segments and subzones of the arterial system.

Skeleton formation and its proper functioning is possible thanks to specialized bone tissue cells: bone forming osteoblasts, bone resorbing osteoclasts and osteocytes located in bone cavities. Gap junctions are transmembrane channels connecting neighboring cell. Thanks to gap junctions it is possible for signals to be directly transmitted by cells. Gap junction type channels, and more specifically the connexin proteins that build them, have a key impacton the bone turnover process, and thus on both bone building and remodeling. A particularly important connexin in bone tissue is connexin43 (Cx43), which is necessary in the proper course of the bone formation process and in maintaining bone homeostasis. The importance of the presence of Cx43 in bones is showed by skeletal defects in diseases such as ODD syndrome and craniometaphyseal dysplasia caused by mutations in GJA1, the gene encoding Cx43. The role of Cx43 in the differentiation of stem cells into bone cells, anti-apoptotic action of bisphosphonates and bone responses to hormonal and mechanical stimuli have also been demonstrated. In addition to connexin43, the presence of other connexins such as connexin45, 46 and 37 was also noted in bone tissue.

Gap junction channels permit the direct intercellular transfer of ions and small molecules and allow electrotonic coupling within tissues. Porcine aortic endothelial cells were extensively coupled, as assessed by gap junctional transfer of Lucifer yellow and the fluorescent calcium indicators fluo-3 and furaptra, but were not permeable to rhodamine B isothiocyanate-dextran 10S. The subunit composition of gap junction channels of porcine aortic endothelial cells was characterised using both northern blot analysis and RT-PCR techniques. Messenger RNA encoding connexins 37 and 43, but not 26, 32 or 40, were found in freshly isolated and cultured porcine aortic endothelial cells. Western blots using antipeptide antibodies raised to unique sequences of connexins 37, 40 and 43 showed the presence of connexins 37 and 43, but no connexin 40 was detected. Immunostaining with anticonnexin 43 antibodies showed extensive punctate fluorescent decoration of contacting membranes, whilst antibodies to connexin 37 showed predominantly intracellular staining. Caged InsP3 was found to readily permeate endothelial gap junctions. These results show that primary cultures of porcine aortic endothelial cells express connexin 37 and 43, and provide strong evidence that the second messenger molecule InsP3 can permeate porcine endothelial gap junctions.

Vascular conducted responses are believed to play a central role in controlling the microcirculatory blood flow. The responses most likely spread through gap junctions in the vascular wall. At present, four different connexins (Cx) have been detected in the renal vasculature, but their role in transmission of conducted vasoconstrictor signals in the preglomerular arterioles is unknown. Connexin mimetic peptides were previously reported to target and inhibit specific connexins. We, therefore, investigated whether conducted vasoconstriction in isolated renal arterioles could be blocked by the use of mimetic peptides directed against one or more connexins. Preglomerular resistance vessels were microdissected from kidneys of Sprague-Dawley rats and loaded with fura 2. The vessels were stimulated locally by applying electrical current through a micropipette, and the conducted calcium response was measured 500 μm from the site of stimulation. Application of connexin mimetic peptides directed against Cx40, 37/43, 45, or a cocktail with equimolar amounts of each, did not inhibit the propagated response, whereas the nonselective gap junction uncoupler carbenoxolone completely abolished the propagated response. However, the connexin mimetic peptides were able to reduce dye coupling between rat aorta endothelial cells shown to express primarily Cx40. In conclusion, we did not observe any attenuating effects on conducted calcium responses in isolated rat interlobular arteries when exposed to connexin mimetic peptides directed against Cx40, 37/43, or 45. Further studies are needed to determine whether conducted vasoconstriction is mediated via previously undescribed pathways.

In addition to providing a pathway for intercellular communication, the gap junction-forming proteins, connexins, can serve a growth-suppressive function that is both connexin and cell-type specific. To assess its potential growth-suppressive function, we stably introduced connexin 37 (Cx37) into connexin-deficient, tumorigenic rat insulinoma (Rin) cells under the control of an inducible promoter. Proliferation of these iRin37 cells, when induced to express Cx37, was profoundly slowed: cell cycle time increased from 2 to 9 days. Proliferation and cell cycle time of Rin cells expressing Cx40 or Cx43 did not differ from Cx-deficient Rin cells. Cx37 suppressed Rin cell proliferation irrespective of cell density at the time of induced expression and without causing apoptosis. All phases of the cell cycle were prolonged by Cx37 expression, and progression through the G1/S checkpoint was delayed, resulting in accumulation of cells at this point. Serum deprivation augmented the effect of Cx37 to accumulate cells in late G1. Cx43 expression also affected cell cycle progression of Rin cells, but its effects were opposite to Cx37, with decreases in G1 and increases in S-phase cells. These effects of Cx43 were also augmented by serum deprivation. Cx-deficient Rin cells were unaffected by serum deprivation. Our results indicate that Cx37 expression suppresses cell proliferation by significantly increasing cell cycle time by extending all phases of the cell cycle and accumulating cells at the G1/S checkpoint.

Gap junctions are intercellular channels that mediate cell-to-cell communication, allowing the passage of small signalling molecules. In the ovary, connexin 43 (Cx43) and connexin 37 (Cx37) are important gap junctional proteins expressed in the granulosa and cumulus cells or oocytes of several species. Gap junctions and connexins are required for the regulation of the oocytes meiotic resumption in preovulatory follicles after the surge of LH. However, unlike other species, canine oocytes do not resume meiosis before ovulation, which could be related to expression patterns of Cx43 and Cx37 during oocyte development and ovulation. Therefore, this study aimed to address the canine Cx37 and Cx43 gene expressions throughout the oestrous cycle, including the preovulatory period. The ovaries were obtained from bitches 1-6 years old (n=72) following ovariohysterectomy. The stage of the oestrous cycle was assessed according the ovarian structures and by measurements of serum progesterone (P4) levels obtained from blood samples on the day of surgery. Anestrus was <0.1 ng/mL P4 and absence of follicles or corpus luteum in the ovarian surface; proestrus was 0.2-2 ng/mL P4 and growing small to medium follicles on the surface of the ovaries; oestrus was 2-19 mg/mL P4 and large follicles on the surface of the ovaries; and diestrus was >20 ng/mL P4 and mainly predominant corpus luteum on the ovaries. For Cx43 analysis, follicular cells (granulosa and theca) were mechanically recovered from follicles (n=620) distributed into 4 types: prenatal (1 layer of granulosa cells up to the onset of antrum formation), small antral (~0.2-0.39mm), medium antral (~0.4-5.9mm), and large antral (~6-10mm). For Cx37 study, the cumulus-oocytes complexes (COC) from the same follicles were used. Total RNA extraction was performed, and the evaluation of gene expression levels was achieved by relative quantification quantitative PCR analysis in follicular cells and COC. The data from at least 3 independent experiments for each gene were evaluated by ANOVA. The gene expression of both Connexins were observed in all stages of follicular development; however, the mRNA levels varied over the oestrous cycle. Both Cx43 and Cx37 transcripts showed the highest (P<0.05) levels at anestrus when compared to other phases. The mRNA levels of both genes remained without changes in large follicles at oestrus stage, suggesting that, in contrast to other mammals where LH down-regulates connexins expression leading to the subsequent loss of intercellular coupling, the communication between the oocyte and follicular cells was maintained in canines. In conclusion, these 2 connexin genes were differentially expressed in canine follicular cells and COC during the follicular development. The maintenance of the gene expression of these connexins at the final follicular growth may be involved in the prolonged meiotic arrest in this species. Supported by Ga grant from FONDECYT (1171670).

The incidence of chronic kidney disease (CKD) is growing worldwide due to the increase of life expectancy, improved survival from cardiovascular diseases and spreading of type-2 diabetes. CKD is characterized by chronic inflammation and accumulation of extracellular matrix components, resulting in alterations within all renal compartments. This leads to the progressive decline of renal function. Presently, no effective means are available to reverse the primary disease process. Moreover, a significant proportion of these patients develop end-stage renal disease. Thus, arresting or reversing the progression of renal disease represents one of the major public health challenges, requiring the discovery of new therapeutic targets in order to combat this disease. Connexins (Cx) are crucial for cell homeostasis and could be considered among the mediators of renal function and/or dysfunction due to their ability to regulate multiple physiopathological signals. Cxs is a family of around 20 transmembrane proteins which form gap junctions and direct cell-to-cell communication in many tissues. Missregulation of Cxs expression has been reported to be implicated in the development of several diseases. We have recently demonstrated that the expression of Cx43 and Cx37 was altered in early stages of experimental nephropathy in mice. The aim of this work was to investigate whether Cx43 and Cx37 participate to the progression of CKD in animal models. We initially explored the role of Cx43 in three experimental models targeting three different renal compartments. Interestingly, when Cx43 was targeted using genetic or pharmacogenetic approaches, we observed a protection of kidney structure and function mainly due to decrease of inflammation and fibrosis. Next, we investigated the possible physiological and pathological roles of Cx37 in tubular epithelial cells by using Cx37 KO mice. Under physiological conditions, mice lacking Cx37 presented a mild renal function phenotype, possibly related to purinergic signaling in distal nephron segments. In addition, these mice were relatively protected against obstructive nephropathy indicating that Cx37 is involved in renal tubular dysfunction. This work demonstrates that Cxs may represent new therapeutic targets against the progression of kidney disease. Further mechanistic studies are necessary to support our observations and to better understand the role of these proteins in CKD
L’incidence de l’insuffisance rénale chronique (IRC) s’accroît dans le monde entier à cause du vieillissement de la population, de l’amélioration de la survie aux maladies cardio-vasculaires et du développement du diabète de type 2. L’IRC se caractérise par une inflammation chronique et une accumulation excessive de matrice extracellulaire, associées à des altérations des différents compartiments du rein. Cela conduit à un déclin progressif de la fonction rénale. Dans de nombreux cas, il n’existe pas de moyen efficace pour inverser le processus pathologique primaire et la majorité de ces patients progressent vers le stade terminal de l’IRC. Par conséquent, de nouveaux médiateurs, et donc de nouvelles cibles thérapeutiques sont indispensables pour lutter contre cette maladie. Les connexines (Cx) jouent un rôle crucial dans l’homéostasie cellulaire et pourraient être considérées parmi les médiateurs de la fonction et/ou dysfonction rénale en raison de leur capacité à réguler de multiples signaux physiopathologiques. Il existe 20 différentes Cx, toutes membres de la famille des protéines transmembranaires formant les jonctions gap. Le dérèglement de l’expression des Cx est connu pour être impliqué dans le développement de plusieurs pathologies. Récemment, nous avons démontré que l’expression des Cx43 et Cx37 est altérée durant les stades précoces de la néphropathie expérimentale murine. L’objectif de cette étude est de déterminer si les Cx43 et Cx37 participent à la progression de l’IRC dans des modèles animaux. Dans un premier temps, nous avons exploré le rôle de la Cx43 dans trois modèles expérimentaux ciblant trois différents compartiments du rein. Ainsi, en ciblant la Cx43 via une approche génétique ou pharmacogénétique, nous avons pu protéger la structure du rein et préserver sa fonction, principalement grâce à une diminution du degré d’inflammation et de fibrose. Dans un second temps, nous avons étudié le rôle physiopathologique de la Cx37 dans les cellules épithéliales tubulaires en utilisant des souris Cx37 KO. En conditions physiologiques, ces souris présentaient un léger phénotype de la fonction rénale possiblement lié à la signalisation purinergique dans les segments distaux du néphron. De plus, ces souris étaient relativement protégées contre la néphropathie obstructive, indiquant que la Cx37 est aussi impliquée dans la dysfonction tubulaire rénale. Ce travail démontre que les Cx pourraient représenter des cibles thérapeutiques prometteuses contre la progression de la maladie rénale. Toutefois, des études mécanistes supplémentaires sont nécessaires pour appuyer nos observations et pour mieux comprendre le rôle des ces protéines dans l’IRC

Whereas Cx43 expression has no effect on proliferation of Rin cells, Cx37 exerts a potent growth suppressive effect on these cells. To determine how Cx37 suppresses growth and whether coexpression of Cx43 altered the suppressive effects of Cx37, two cell lines were created. 43tet/37 C4 cells constitutively express Cx43 and the tet-on transcription factor, which supports tetractycline inducible Cx37 expression in these cells. i43/i37 D6 cells constitutively express the tet-on transcription factor, which supports inducible expression of both connexins. The 43tet/37 C4 cells exhibit high Cx43:Cx37 expression ratio, whereas the i43/i37 D6 cells have a low Cx43:Cx37 expression ratio. In both cell lines, Cx37 and Cx43 appear (by reciprocal coimmunoprecipitation experiments) to form heteromeric channels. The proliferative properties of the co-expressing cell lines show that Cx37 growth suppression in Rin cells is relieved in a dose dependent manner by the presence of Cx43. In contrast, we demonstrate that 14-3-3σ may play a role in the growth suppressive mechanism of Cx37 in Rin cells as it is upregulated in cells expressing Cx37 and has the capability of binding to Cx37, presumably at the consensus binding motif in the C-terminus.

Connexins are a family of gene products sharing a similar topology that mediate transmembrane and intercellular diffusion of ions and small molecules through hemichannels (HCs) and gap junction channels (GJCs), respectively, and participate in intracellular signaling through protein-protein interaction. Connexin 37 (Cx37) and Cx40 are co-expressed by endothelial cells, suggesting a unique role for each connexin in regulating cellular function. Through gene knockout studies in mice, Cx37 was found to regulate vascular cell proliferation while Cx40 regulates conduction of upstream vasomotor signals and leukocyte infiltration. The unique functions of Cx37 and Cx40 result in contrasting effects of ischemic injury in mice lacking expression of either Cx37 or Cx40 genes. Cx37 knockout mice (Cx37-/-) have significantly improved recovery due to an increase in both vasculogenesis and angiogenic processes. In the current studies, the mechanism by which Cx37 mediates cellular proliferation is explored by examining the role of functional GJCs and HCs. Channel function is necessary, but HC function is not sufficient for Cx37-mediated suppression of proliferation. These results suggest that Cx37 requires a competent GJC that supports a specific conformation of the carboxyl terminus that is able to interact with necessary growth regulatory protein(s). Conversely, Cx40-/- mice have reduced angiogenic and arteriogenic processes and impaired post-ischemic recovery. In the current study, we explored the inflammatory response following the femoral artery ligation (FAL) surgery, in wildtype (WT) and Cx40-/- mice. Cx40-/- mice had an excessive infiltration of activated neutrophils to the ischemic gastrocnemius muscle and a prolonged presence of activated macrophages. We depleted mice of circulating neutrophils during the induction of ischemia to evaluate if the excessive infiltration of neutrophils impaired recovery and found no improvement in post-ischemic recovery in either WT or Cx40-/- mice. These data indicate that, although Cx40-/- mice have a pro-inflammatory state that results in an excessive and prolonged presence of leukocytes post-ischemia, reduction of acute leukocyte infiltration does not improve post-ischemic recovery. Additional information is necessary to determine the mechanisms by which Cx37 and Cx40, individually or in concert with each other, regulate endothelial cell function and arterial vascular response to ischemic injury.

Connexins support the coordinated function of virtually all tissues in the body through facilitation of intercellular, transmembrane, and intracellular signaling. Connexin 37 (Cx37), which plays a role in vascular development and remodeling, has growth suppressive properties that depend on its channel function and the presence and phosphorylation status of its carboxylterminus (CT). In settings of injury, Cx37 expression is reduced - a change permissive to vascular repair. Serine 319 (S319) is a high probability (>90%) target for phosphorylation by growth factor-activated kinases, and the phosphorylation status of this site is important to the inflammatory response to injury and atherosclerosis. Here, we substituted S319 with alanine or aspartate, to mimic the dephosphorylated (S319A) and phosphorylated (S319D) states, respectively, and transfected rat insulinoma (Rin) cells with these mutants to elucidate the mechanistic basis for phospho-form specific roles of Cx37-S319 in growth control. Both mutants formed functional gap junction channels, but Cx37-S319A relieved the growth suppressive effect of Cx37, whereas Cx37-S319D did not. Altogether, these data suggest that preventing phosphorylation at S319 is sufficient to relieve the growth suppressive effect of Cx37, but the mechanistic basis for this effect is likely through induced changes in protein-protein interactions.

Connexin 37 (Cx37), profoundly suppresses the growth of rat insulinoma (Rin) cells and requires a functional channel. To determine if the CT is necessary for Cx37-mediated growth suppression, a series of deletions and mutations affecting the availability of putative phosphorylation sites in the region of 273-333 of Cx37 were generated. Truncation at P273 alleviated the growth suppressive effect of Cx37 while retaining channel functionality. Interestingly, substate behavior is lost in iRin37-273tr. Based on the observation of run-down behavior in Cx37-wt channels consistent with dialysis of PKC, TPA and BIM treatment of Cx37- wt channels revealed that PKC activation generates a higher incidence of high conductance channels whereas BIM treatment results in the converse. Exploiting this observation, a S-Ax3 mutation targeting known MAPK and PKC sites aligned from Cx43, was generated. However, channels are able to reside in the sub-conductance state and cells are anti-proliferative. Four additional serine to alanine mutations at putative phosphorylation sites (>90%) were made to generate an S7A mutation and did not dispel the growth suppressive effect of Cx37. A phosphomimetic S7D mutation appears to induce cell death. Based on these data, it appears that substate behavior regulated by the CT is indicative growth suppression by Cx37.

Gap junction channels (GJChs) support the coordination of vascular responses required for the control of normal vascular function by providing a pathway for intercellular diffusion of ions and small molecules. Made of connexin proteins, dysregulation (changes in expression, localization, and function) of gap junction channels or hemichannels (HChs) contribute to and/or exacerbate vascular disease. Specifically, Cx37 is enriched at endothelial cell borders under laminar flow conditions, but is downregulated in regions of oscillatory shear stress, like that occurring downstream of an atherosclerotic plaque. We showed that Cx37 limits vasculogenesis and ischemia-induced angiogenesis, likely by reducing proliferation and enhancing cell death of endothelial cells. Moreover, these Cx37-mediated growth effects require a functional pore-forming domain and the presence of its own carboxyl-terminus (CT). As phosphorylation has been shown to influence channel conductance and growth regulatory properties of other connexins, we hypothesized that differential phosphorylation of the Cx37 carboxyl-terminus regulates channel function and its growth effects. Using alanine (or phenylalanine) and aspartate substitutions to mimic dephosphorylated or phosphorylated amino acid residues, respectively, we show herein that Cx37 may serve as a molecular switch that contributes to cell fate decisions (quiescence versus cell cycle progression and cell death) in a phosphorylation-dependent manner. Moreover, Cx37 GJCh and HCh function is modulated by site-specific phosphorylation within the CT. While channel function is necessary for Cx37-mediated growth effects, it appears that protein-protein interactions (rather than channel-dependent functions) with phosphorylation-specific conformations of Cx37 and growth regulatory elements determine growth phenotype.

Este trabajo de tesis doctoral “Aproximación a la relación entre el conocimiento del profesor y el establecimiento de conexiones en el aula” representa una aportación a la investigación en Educación Matemática, y en particular al estudio del conocimiento del profesor. A partir del análisis de diferentes modelos para el conocimiento del profesor, se constata la existencia de una relación explícita entre el conocimiento del profesor y las conexiones. En consecuencia, se plantea la siguiente pregunta de investigación: ¿Cómo influye el conocimiento del profesor de matemáticas en el establecimiento de conexiones en el aula? Para dar respuesta a esta pregunta se plantean los siguientes objetivos de investigación: 1) Identificar conexiones que se establecen en sesiones reales de aula y analizar sus características; 2) Construir una definición de conexión matemática desde una perspectiva práctica en un contexto de aula y establecer criterios de clasificación para las conexiones en un contexto de aula; 3) Relacionar tipologías de conocimiento matemático del profesor con las características de cada tipología de conexiones; y 4) Analizar las relaciones que se establezcan entre diferentes tipos de conocimiento del profesor, para el establecimiento de conexiones en el aula. Para la consecución de estos objetivos se analizan sesiones reales de aula de 1º de ESO (12-13 años) en un instituto público de educación secundaria en Barcelona. La fundamentación teórica se divide en dos bloques. En primer lugar se analiza el establecimiento de conexiones desde tres perspectivas que se coordinan en el aula: el contenido matemático, los alumnos y la profesora. En segundo lugar, se discuten diferentes modelos de referencia para el conocimiento. Fruto de la discusión de diversos modelos de referencia se propone una reinterpretación del modelo de Shulman (1986) que considera tres bloques principales en el conocimiento: el conocimiento del contenido, el conocimiento pedagógico del contenido y el conocimiento curricular. Se platea un estudio de caso, en el que se analiza un grupo clase de manera intensiva. Este enfoque metodológico permite obtener datos homogéneos. El análisis de los datos permitió explorar la relación entre conocimiento del profesor y establecimiento de conexiones. Para el análisis de datos relacionado con los dos primeros episodios se realizó una interpretación de la teoría fundamentad, sin seguir rigurosamente todas su etapas. Se realizó una comparación constante y minuciosa entre los resultados parciales y los datos. Este proceso dio como resultado la construcción de una definición de conexión en el aula y la identificación de cuatro tipologías de conexiones. A continuación se identifican indicadores de conocimiento para cada una de las conexiones identificadas. Los resultados de la investigación muestran que existe una estrecha relación entre la discusión explícita de errores de los alumnos y el establecimiento de conexiones en el aula. Así, se consideran las conexiones como redes de enlaces cuya interpretación errónea e incompleta da lugar a errores comunes en la matemática escolar. Se identifican cuatro tipos de conexiones: conexiones extramatemáticas; conexiones intramatemáticas relativas a procesos transversales; conexiones intramatemáticas con conversión y conexiones intramatemáticas con tratamiento. Para cada tipo de conexión se identificaron tipologías de conocimiento que se relacionaban con su establecimiento. Esta relación entre tipologías de conocimiento y el establecimiento de diferentes tipos de conexiones permitió identificar también conocimiento relacionado con el enriquecimiento de las conexiones en términos de aprovechamiento de oportunidades de aprendizaje. Se concluye que existen distintos niveles en el conocimiento del profesor que pueden ser descritos en relación a los tipos de conexiones con que se relacionan y con la profundidad del conocimiento matemático que se construye. La progresión en estos niveles se asocia con la capacidad del profesor para aprovechar las oportunidades que surgen en el aula.
The PhD dissertation “An approach to the relationship between teacher’s knowledge and the making of connections in the classroom” constitutes a contribution to the field of Mathematics Education, particularly to the study of teacher knowledge. The implicit relation between teacher knowledge and connections is identified from a theoretical analysis of different models for teacher knowledge. This relation generated the key research question: ¿How does teacher’s knowledge influence the making of connections in the classroom? To tackle this question, four goals have been posed: 1) To identify connections in a real classroom setting and characterize them; 2) To create a definition of connection from a practical perspective and to establish criteria to classify them; 3) To identify what kinds of teacher’s knowledge are related with each kind of connection; 4) To analyze the links between different kinds of teacher knowledge for the making of connections in the classroom. To achieve these goals eight consecutive sessions from a real class have been analyzed in a public secondary school in Barcelona, with 12 and 13-year-old students. The theoretical framework has two main parts. Firstly, the making of connections is analyzed from three different perspectives considering a classroom context: the mathematical content, the students and the teacher. Secondly, a deep revision of the reference models for teacher knowledge is carried out. As a result of this analysis, a reinterpretation of Shulman’s model (1986) is proposed. The reinterpretation is based on the three original dimensions of teacher knowledge: mathematical content knowledge, pedagogical content knowledge and curriculum knowledge. A case study is conducted. The intensive analysis of the same group during one teaching unit gave homogeneous data. The analysis of the data showed explicit links between knowledge and the making of connections. For the first two goals, the analysis design was inspired by the grounded theory paradigm. The constant and meticulous comparison between partial results and data resulted in the construction of a classification for connections in a classroom environment. Next, indicators of teacher knowledge are identified for each kind of connection. Results showed that there is a strong relationship between the explicit discussion of student’s mistakes in the classroom and the emergence of connections. Thus, connections are considered as a web of links, and it’s incomplete or wrong interpretation produce common misconceptions. Four kinds of connections are identified: extramathematical connections; intramathematical connections related with cross processes; intramathematical connections with conversion; and intramathematical connections with treatment. An explicit relation between each kind of connection and kinds of teacher knowledge is identified, described and discussed. This relation permitted the identification of the kind of knowledge that is related with the enrichment of connections in terms of taking advantage from the learning opportunities. Conclusions suggest that there are different levels in teacher knowledge that can be described in terms of the different kinds of connections and the depth of the mathematical knowledge that is constructed. The progression in these levels is related to the teacher’s capacity to make sophisticated connections and to use the opportunities that emerge from the classroom activity.