GJA1 Research Articles

GJA4 gene inhibition may represent a potential target for novel antithrombotic therapies

Abstract The GJA4 gene encodes a protein called connexin 37, a component of gap junctions in vascular endothelial cells, crucial in regulating endothelial function and influencing inflammation, platelet adhesion and thrombus formation. This gene deletion in mice diminished thrombus formation in vitro in human blood. In these circumstances, connexin inhibition with pharmacological agents may represent potential avenues for developing novel antithrombotic agents. Aim To investigate whether the GJA4 rs618675 T>C variant is a risk factor for progressing atherosclerosis and cardiovascular (CV) events in an asymptomatic free of apparent CAD from a Portuguese population. Methods A prospective study was performed with 1421 individuals without apparent CV disease (73.6% male, aged 52.2±8.3 years) followed during an extended period of 7.2±5.1 years). GJA4 rs618675 T>C variant was genotyped by TaqMan real-time PCR technique (Applied Biosystems). Conventional, anthropometric, biochemical and clinical risk factors were studied. Bivariate analysis and multivariate Cox regression adjusted for age, gender, traditional risk factors, biochemical markers, and the genotypes under study was performed to determine which variables were, significantly and independently, associated with CV events. Kaplan-Meier's estimate assessed the prognosis. Results Bivariate analysis showed that 50.6% of wild genotype (TT) carriers had CV events vs. 66.2% without events. Of the risk genotype (CC) carriers, 10.1% had CV events, and 3.4% did not. After the Kaplan-Meier analysis, the TT carriers had 90% CV event-free survival time and the CC risk carriers had only 64% of event-free survival. Finally, after adjustment, CC genotype remained in the equation with an HR of 3.1 (p=0.003) and CT heterozygous with HR of 1.6 (p=0.043), together with Hypertension (HR 3.0; p<0.0001), Smoking habits (HR 2.3; p=0.001) and Diabetes (HR 1.9; p=0.015). Conclusion: The CC risk genotype of the GJA4 rs618675 represented an independent risk factor for progressing atherosclerosis and CV events in a Portuguese Population. Thrombus formation often begins with the adhesion of platelets to the endothelium, and connexin 37 may influence this process. The inhibition of connexin 37 emerges as a promising candidate for future cardiovascular prevention as well as for the development of new antithrombotic drugs.

Study of the role of leukocyte telomere length-related lncRNA NBR2 in Alzheimer's disease.

Alzheimer's Syndrome (AD) is a neurodegenerative disease that is prevalent in middle-aged and elderly people. As the disease progresses, patients gradually lose the ability to take care of themselves, which brings a heavy burden to the family. There is a link between leukocyte telomere length (LTL) and cognitive ability. To search for possible pathogenic mechanisms and potential therapeutic agents, we demonstrated a causal link between LTL and AD using Mendelian randomization analysis (MR). The expression of the target gene NBR2 and the downstream mRNA GJA1 and GJA1-related genes, pathway enrichment, and association with immune cells were further explored. Using the gene cluster-drug target interaction network, we obtained potential therapeutic drugs. Our study provides evidence for a causal link between AD and LTL, suggesting medicines that may treat and alleviate AD symptoms.

Anakinra Promotes M2 Microglia Activation during the Latent Phase of the Lithium-Pilocarpine Model of Temporal Lobe Epilepsy

Astrocytes and microglia and their polarization are thought to contribute to the progression of epilepsy. One of the processes affecting polarization is neuroinflammation, which plays an important role in epileptogenesis. However, the specific mechanisms of its involvement in shifting the pro- and anti-inflammatory reactivation of astro- and microglia have not been clarified. In this study, we examined the effect of 7-day interleukin-1 receptor antagonist (anakinra) administration on glial cell polarization during the latent phase of the lithium-pilocarpine model in 7-week-old male Wistar rats. In temporal cortex, dorsal and ventral hippocampus the mRNA expression levels of the following genes were analyzed: (i) markers of astroglia (S100b) and microglia (Aif1) activation, (ii) astrocytic proteins involved in glutamate transport and metabolism (Slc1a3, Glul, Gja1), (iii) pro-inflammatory pathway interleukin-1β (Nlrp3, Il1b, Il1rn) and transforming growth factor β1 (Tgfb1), (iv) markers of astroglia polarization (Lcn2, S100a10, Gbp2, Ptx3), and (v) microglia polarization (Nos2 and Arg1). The mRNA expression levels of S100b and Aif1 were significantly increased, and anakinra administration did not reduce their overexpression. This indicates reactivation of astroglia and microglia regardless of the anakinra administered. The expression of Slc1a3, Glul, and Gja1 genes increased in the hippocampus; anakinra administration did not affect their hyperexpression, but promoted increased expression of Gja1 in the temporal cortex. The mRNA production of Lcn2, S100a10, Gbp2, Ptx3, Nlrp3, Il1b, Il1rn and Tgfb1 increased in all structures. Administration of anakinra reduced the gene expression of Il1b. Among the markers of microglia polarization, downregulation of Arg1 expression in the dorsal hippocampus and Nos2 expression in the temporal cortex was detected. Anakinra administration enhanced the decrease in Nos2 expression and restored the level of Arg1 expression to control values. Thus, anakinra administration did not affect the intensity of glial cell reactivation, but improved M2 reactivation of microglia.

Connexin 43 Modulation in Human Chondrocytes, Osteoblasts and Cartilage Explants: Implications for Inflammatory Joint Disorders.

Connexin 43 (Cx43) is crucial for the development and homeostasis of the musculoskeletal system, where it plays multifaceted roles, including intercellular communication, transcriptional regulation and influencing osteogenesis and chondrogenesis. Here, we investigated Cx43 modulation mediated by inflammatory stimuli involved in osteoarthritis, i.e., 10 ng/mL Tumor Necrosis Factor alpha (TNFα) and/or 1 ng/mL Interleukin-1 beta (IL-1β), in primary chondrocytes (CH) and osteoblasts (OB). Additionally, we explored the impact of synovial fluids from osteoarthritis patients in CH and cartilage explants, providing a more physio-pathological context. The effect of TNFα on Cx43 expression in cartilage explants was also assessed. TNFα downregulated Cx43 levels both in CH and OB (-73% and -32%, respectively), while IL-1β showed inconclusive effects. The reduction in Cx43 levels was associated with a significant downregulation of the coding gene GJA1 expression in OB only (-65%). The engagement of proteasome in TNFα-induced effects, already known in CH, was also observed in OB. TNFα treatment significantly decreased Cx43 expression also in cartilage explants. Of note, Cx43 expression was halved by synovial fluid in both CH and cartilage explants. This study unveils the regulation of Cx43 in diverse musculoskeletal cell types under various stimuli and in different contexts, providing insights into its modulation in inflammatory joint disorders.

The mechanistic role of connexin 43 in maturation of hiPSC cardiomyocytes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ECR (European research council) and ReNew (the Novo Nordisk Foundation Center for Stem Cell Medicine supported by Novo Nordisk Foundation grants) Introduction Cardiomyocytes (CMs) differentiated from human induced pluripotent stem cells (hiPSCs) are functionally immature and this limits the application of these cells to cardiovascular research. Maturation can be improved by aggregating hiPSC-CMs into three-dimensional (3D) microtissues together with hiPSC-cardiac fibroblasts (hiPSC-CFs) and hiPSC-endothelial cells (hiPSC-ECs). These cardiac microtissues showed improved structural (increase of sarcomere length and organisation) and functional (more mature action potential profile) properties. This effect was only observed when the cardiac microtissues contained hiPSC-CFs. Since connexin 43 (CX43), the most ubiquitous connexin isoform in the heart, was significantly upregulated in hiPSC-CMs from cardiac microtissues, we hypothesise that mechanisms underlying hiPSC-CMs maturation involves the coupling of hiPSC-CMs with hiPSC-CFs through this protein. Purpose The aim of this study is to unravel the role of CX43 in the maturation of hiPSC-CMs in the context of 3D multicellular cardiac tissues. Methods We used the CRISPR/Cas9 technology to generate a CX43 knock-out (KO) hiPSC line. We designed two sgRNAs annealing to exon 2 of GJA1 gene, encoding CX43; indels generated by the non-homologous end joining after the Cas9 double strand break will result in a non-functional protein. Cells were differentiated in vitro into CMs, epicardial cells (EPI) and then CFs and characterized for the expression of cell-specific markers and compared with the wild-type parental control cells. Results and conclusions We screened 31 hiPSC clones and selected those in which both GJA1 alleles contained a deletion. Copy number variation analysis by ddPCR of the flanking regions confirmed that the deletion was specific and confined. The lack of GJA1 expression in the KO clones was confirmed by qPCR, while the lack of the CX43 protein was confirmed by immunofluorescence and Western Blot. This did not affect CX43-KO hiPSCs pluripotency state shown by the presence of pluripotent markers such as NANOG, OCT3/4, SSEA4. Additionally, CX43-KO hiPSCs were able to differentiate into the three germ layers. CX43-KO hiPSCs were successfully differentiated into hiPSC-CMs, -EPI, and -CFs. CX43-KO hiPSC-CMs and controls showed comparable gene expression of cardiac troponin T. Since immunofluorescent staining showed that CX43-KO hiPSC-EPI expressed the epicardial markers WT1 and ZO1, we continued to differentiate them into hiPSC-CFs, which expressed markers such as VIM and COL1A1, similar to the control. Differentiated CX43-KO hiPSC-CMs and CFs will be assembled into cardiac microtissues. Functional and structural assays that include patch-clamp and immunofluorescence will be performed on these microtissue to assess the effect of the CX43 KO on the maturation of hiPSC-CMs. Our results show that the lack of CX43 expression does not impede hiPSCs to differentiate into various cell types originating from the mesoderm germ layer.

Analysis of clinical characteristics and molecular genetics in eighteen patients with 1q21.1 microdeletion syndrome

To explore the clinical characteristics of 1q21.1 microdeletion by using single nucleotide polymorphism microarrays (SNP array). Eighteen cases of 1q21.1 microdeletion syndrome diagnosed at the Longgang District Maternal and Child Health Care Hospital of Shenzhen City from June 2017 to December 2022 were selected as the study subjects. Clinical data of the patients were collected. Results of chromosomal karyotyping and SNP assay were retrospectively analyzed. Among the 18 cases with 1q21.1 microdeletions, 13 had a deletion between BP3 and BP4, 4 had a deletion between BP1/BP2 and BP4, whilst 1 had a proximal 1q21.1 deletion (between BP2 and BP3) involving the Thrombocytopenia-absent radius (TAR) region. The deletions had spanned from 360 kb to 3.9 Mb, which encompassed the GJA5, GJA8, CHD1L, RBM8AB and other morbid genes. In three families, the proband child has inherited the same 1q21.1 microdeletion from their parents, whose clinical phenotype was normal or slightly abnormal. The clinical phenotypes of 1q21.1 microdeletion had included cognitive or behavioral deficits in 9 cases (9/18, 50.0%), growth retardation in 8 cases (8/18, 44.4%), craniofacial deformities in 7 cases (7/18, 38.8%), cardiovascular malformations in 5 cases (5/18, 27.8%), and microcephaly in 3 cases (3/18, 16.7%). 1q21.1 microdeletion syndrome has incomplete penetrance and varied expression such as intellectual impairment, growth and development delay, and microcephaly, with a wide range of non-specific phenotypes.

Effect of Cyclic Adenosine Monophosphate on Connexin 37 Expression in Sheep Cumulus-Oocyte Complexes.

Gap junctional connection (GJC) in the cumulus-oocyte complex (COC) provides necessary support for message communication and nutrient transmission required for mammalian oocyte maturation. Cyclic adenosine monophosphate (cAMP) is not only a prerequisite for regulating oocyte meiosis, but also the key intercellular factor for affecting GJC function in COCs. However, there are no reports on whether cAMP regulates connexin 37 (Cx37) expression, one of the main connexin proteins, in sheep COCs. In this study, the expression of Cx37 protein and gene in immature sheep COC was detected using immunohistochemistry and PCR. Subsequently, the effect of cAMP on Cx37 expression in sheep COCs cultured in a gonadotropin-free culture system for 10 min or 60 min was evaluated using competitive ELISA, real-time fluorescent quantitative PCR (RT-qPCR), and Western blot. The results showed that the Cx37 protein was present in sheep oocytes and cumulus cells; the same results were found with respect to GJA4 gene expression. In the gonadotropin-free culture system, compared to the control, significantly higher levels of cAMP as well as Cx37 gene and protein expression were found in sheep COCs following treatment in vitro with Forskolin and IBMX (100 μM and 500 μM)) for 10 min (p < 0.05). Compared to the controls (at 10 or 60 min), cAMP levels in sheep COCs were significantly elevated as a result of Forskolin and IBMX treatment (p < 0.05). Following culturing in vitro for 10 min or 60 min, Forskolin and IBMX treatment can significantly promote Cx37 expression in sheep COCs (p < 0.05), a phenomenon which can be counteracted when the culture media is supplemented with RP-cAMP, a cAMP-specific competitive inhibitor operating through suppression of the protein kinase A (PKA). In summary, this study reports the preliminary regulatory mechanism of cAMP involved in Cx37 expression for the first time, and provides a novel explanation for the interaction between cAMP and GJC communication during sheep COC culturing in vitro.

Sertoli cell-conditioned medium can improve blood-testis-barrier function and spermatogenesis in azoospermia mice induced by scrotal hyperthermia: An experimental study.

An increase in the temperature of the testis is associated with damage to the epithelium of seminiferous tubules and disruption of sperm production. The current study aimed to investigate the effect of the Sertoli cell-conditioned medium (SCCM) on the blood-testis-barrier associated genes and spermatogenesis process following scrotal hyperthermia. In this experimental study, 40 adult NMRI mice (8 wk, 25-30 gr) were allocated into 4 groups: I) control, II) DMEM (10 μl Dulbecco's Modified Eagle Medium), III) scrotal hyperthermia, and IV) scrotal hyperthermia+SCCM (10 μl SCCM). Hyperthermia was induced by placing the mice scrotum in water at 43 C for 20 min every other day for 10 days. Mice were treated every other day for 5 wk. Then the animals were euthanized, and the tails of epididymis were removed to analyze sperm parameters, testis were taken for stereological assessment, reactive oxygen spices and glutathione levels, and the expression of Ocln, Gja1, Cdh2, and Itgb1. The results of sperm analysis indicated that SCCM-treated mice significantly increased sperm count and motility and reduced DNA fragmentation. In addition, histological and molecular findings showed that the volume of testicular tissue, the number of germ cells, the glutathione level, and the expression of Ocln, Gja1, Cdh2, and Itgb1 genes were significantly increased in the SCCM-treated mice. Findings suggest that growth factors of SCCM stimulate the proliferation and differentiation of germ cells through paracrine effects and upregulate the blood-testis-barrier-associated genes in mice subjected to scrotal hyperthermia.

The Expression Analysis of MEST1 and GJA1 Genes in Gastric Cancer in Association with Clinicopathological Characteristics.

Background: Gastric cancer is an invasive cancer, which is usually diagnosed in advanced stages. However, the markers affecting its progression, and invasion are of great importance in its diagnosis and treatment. The current research aimed to study the correlation of genes that contributed to epithelial-mesenchymal transition (EMT), Mest1, and GjA1, with some clinicopathological specifications in gastric cancer patients to better comprehend the functions of these genes in this tumor. Materials and Methods: RNA was extracted from the tumor, and normal tissues and cDNA were synthesized. Then, by designing specific primers for Gja1 and Mest1 genes, their expressions were studied by RT-PCR. The data was analyzed by GraphPad Prism 8 software. Results: Significant differences among the expressions of mentioned genes associated with clinicopathological variables of gastric cancer patients, including tumor size, grade, stage, metastasis, and lymphatic invasion were seen. Conclusion: The obtained data showed the important role of EMT-related genes, Gja1 and Mest1 in the clinical progression of the tumor. Further studies with larger sample sizes are required to confirm these genes as biomarker candidates for detecting gastric cancer.

Mapping the Anti-Cancer Activity of α-Connexin Carboxyl-Terminal (aCT1) Peptide in Resistant HER2+ Breast Cancer.

Connexin 43 (Cx43) is a protein encoded by the GJA1 gene and is a component of cell membrane structures called gap junctions, which facilitate intercellular communication. Prior evidence indicates that elevated GJA1 expression in the HER2-positive (HER2+) subtype of breast cancer is associated with poor prognosis. Prior evidence also suggests that HER2+ breast cancers that have become refractory to HER2-targeted agents have a loss of Cx43 gap junction intercellular communication (GJIC). In this study, a Cx43-targeted agent called alpha-connexin carboxyl-terminal peptide (aCT1) is examined to determine whether GJIC can be rescued in refractory HER2+ breast cancer cells. A proposed mechanism of action for aCT1 is binding to the tight junction protein Zonal Occludens-1 (ZO-1). However, the true scope of activity for aCT1 has not been explored. In this study, mass spectrometry proteomic analysis is used to determine the breadth of aCT1-interacting proteins. The NanoString nCounter Breast Cancer 360 panel is also used to examine the effect of aCT1 on cancer signaling in HER2+ breast cancer cells. Findings from this study show a dynamic range of binding partners for aCT1, many of which regulate gene expression and RNA biology. nCounter analysis shows that a number of pathways are significantly impacted by aCT1, including upregulation of apoptotic factors, leading to the prediction and demonstration that aCT1 can boost the cell death effects of cisplatin and lapatinib in HER2+ breast cancer cells that have become resistant to HER2-targeted agents.

GJB2 c.35del variant up-regulates GJA1 gene expression and affects differentiation of human stem cells.

Pathogenic DNA alterations in GJB2 are present in nearly half of non-syndromic hearing loss cases with autosomal recessive inheritance. The most frequent variant in GJB2 causing non-syndromic hearing loss is the frameshifting c.35del. GJB2 encodes Cx26, a protein of the connexin family that assembles hemichannels and gap junctions. The expression of paralogous proteins is believed to compensate for the loss of function of specific connexins. As Cx26 has been involved in cell differentiation in distinct tissues, we employed stem cells derived from human exfoliated deciduous teeth (SHEDs), homozygous for the c.35del variant, to assess GJB2 roles in stem cell differentiation and the relationship between its loss of function and the expression of paralogous genes. Primary SHED cultures from patients and control individuals were compared. SHEDs from patients had significantly less GJB2 mRNA and increased amount of GJA1 (Cx43), but not GJB6 (Cx30) or GJB3 (Cx31) mRNA. In addition, they presented higher induced differentiation to adipocytes and osteocytes but lower chondrocyte differentiation. Our results suggest that GJA1 increased expression may be involved in functional compensation for GJB2 loss of function in human stem cells, and it may explain changes in differentiation properties observed in SHEDs with and without the c.35del variant.

Cyclic AMP mediates ovine cumulus-oocyte gap junctional function via balancing connexin 43 expression and phosphorylation.

Gap junction channels in cumulus-oocyte complexes (COCs) enable the transmission and communication of small molecular signals between adjacent cells, such as cAMP. However, the regulation of gap junction function (GJF) by cAMP and the underlying mechanisms involved are not fully clarified. This study investigated the effect of cAMP on connexin 43 (CX43) expression and GJF in ovine COCs using immunofluorescence, quantitative real-time PCR (qRT-PCR), western blotting, and GJF detection. The CX43 was only found in the cumulus cells (CCs) side of ovine COC. The intra-oocyte cAMP showed a significant increase at 30 min, while the intra-CC cAMP exhibited two peaks at 10 min and 1 h during in vitro maturation (IVM). Phosphorylated CX43 protein exhibited an immediate increase at 10 min, and CX43 protein displayed two peaks at 10 min and 1 h during IVM. The duration of pre-IVM exposure to forskolin and IBMX significantly enhanced phosphorylated and total CX43, as well as Gja1 and Creb genes, for 10 min; these effects were counteracted by Rp-cAMP. Both pre-IVM with forskolin and IBMX for 1 h and the GJF and CX43/p-CX43 ratio were elevated. The closure of gap junction channels caused by phosphorylated CX43 to prevent cAMP outflow from oocytes in early IVM of COC. Cyclic AMP upregulated phosphorylated and total CX43 via genomic and non-genomic pathways, but its functional regulation was dependent on the balance of the two proteins. This study provides a new insight into the regulatory mechanism between cAMP and GJF, which would improve IVM in animal and clinical research.

Potential of GJA8 gene variants in predicting age-related cataract: A comparison of supervised machine learning methods.

Cataracts are the problems associated with the crystallins proteins of the eye lens. Any perturbation in the conformity of these proteins results in a cataract. Age-related cataract is the most common type among all cataracts as it accounts for almost 80% of cases of senile blindness worldwide. This research study was performed to predict the role of single nucleotide polymorphisms (SNPs) of the GJA8 gene with age-related cataracts in 718 subjects (400 age-related cataract patients and 318 healthy individuals). A comparison of supervised machine learning classification algorithm including logistic regression (LR), random forest (RF) and Artificial Neural Network (ANN) were presented to predict the age-related cataracts. The results indicated that LR is the best for predicting age-related cataracts. This successfully developed model after accounting different genetic and demographic factors to predict cataracts will help in effective disease management and decision-making medical practitioner and experts.

GJA3 Genetic Variation and Autosomal Dominant Congenital Cataracts and Glaucoma Following Cataract Surgery

The p.Asp67Tyr genetic variant in the GJA3 gene is responsible for congenital cataracts in a family with a high incidence of glaucoma following cataract surgery. To describe the clinical features of a family with a strong association between congenital cataracts and glaucoma following cataract surgery secondary to a genetic variant in the GJA3 gene (NM_021954.4:c.199G>T, p.Asp67Tyr). This was a retrospective, observational, case series, genetic association study from the University of Iowa spanning 61 years. Examined were the ophthalmic records from 1961 through 2022 of the family members of a 4-generation pedigree with autosomal dominant congenital cataracts. Frequency of glaucoma following cataract surgery and postoperative complications among family members with congenital cataract due to the p.Asp67Tyr GJA3 genetic variant. Medical records were available from 11 of 12 family members (7 male [63.6%]) with congenital cataract with a mean (SD) follow-up of 30 (21.7) years (range, 0.2-61 years). Eight of 9 patients with congenital cataracts developed glaucoma, and 8 of 8 patients who had cataract surgery at age 2 years or younger developed glaucoma following cataract surgery. The only family member with congenital cataracts who did not develop glaucoma had delayed cataract surgery until 12 and 21 years of age. Five of 11 family members (45.5%) had retinal detachments after cataract extraction and vitrectomy. No patients developed retinal detachments after prophylactic 360-degree endolaser. The GJA3 genetic variant, p.Asp67Tyr, was identified in a 4-generation congenital cataract pedigree from Iowa. This report suggests that patients with congenital cataract due to some GJA3 genetic variants may be at especially high risk for glaucoma following cataract surgery. Retinal detachments after cataract extraction in the first 2 years of life were also common in this family, and prophylactic retinal endolaser may be indicated at the time of surgery.

Transforming Growth Factor ß1 and Gap Junction Protein Alpha 4 Gene Heterogeneity in Relation to the Severity of Clinical Disease in Cystic Fibrosis.

High TGFβ1-producing variants cause severe clinical disease in F508del homozygous patients. Lately, we showed that a single nucleotide polymorphism (SNP), rs41266431, in the GJA4 gene modifies the disease severity of cystic fibrosis (CF). Our aim was to investigate whether the clinical phenotype associated with GJA4 variants was independent of TGFβ1 variants. Homozygous F508del patients (n = 115, mean age 27.2 years, m/f (65/50)) were included in this study. A deep sequence analysis was performed for GJA4 and TGBβ1, and disease severity was assessed over 3 years using lung function tests (LFTs), body mass index, diabetes mellitus, colonization with Pseudomonas aeruginosa, survival to end-stage lung disease (ESLD), as well as distinct inflammatory biomarkers. The analyses revealed that one SNP (rs41266431) in GJA4 may be clinically relevant. Carriers homozygous for the G variant (n = 84; 73%) presented with worse LFTs (forced vital capacity (FVC) % predicted: mean 80/86.6, p < 0.035) and a lower survival to ESLD (p < 0.029). For the TGBβ1 variant: 509 carriers of the C variant (CT + CC genotype, n = 105, 91.3%) had better LFTs (Forced expiratory flow at 75% of the FVC (FEF75% predicted: median 40/29.5, p < 0.015), although a similar outcome to ESLD. A gene-gene interaction was not observed between TGBβ1 and GJA4 variants for any clinical measure. GJA4 variants are independent of TGBβ1 variants. Both variants had an impact on the LFTs, although only GJA4 variants were associated with an improved outcome for ESLD. The study was registered with ClinicalTrials.gov, number NCT04242420, retrospectively on January 24th, 2020.

Study of The Molecular Nature of Congenital Cataracts in Patients from The Volga–Ural Region

Hereditary cataracts are characterized by significant clinical and genetic heterogeneity, which can pose challenges for early DNA diagnosis. To comprehensively address this problem, it is essential to investigate the epidemiology of the disease, perform population studies to determine the spectrum and frequencies of mutations in the responsible genes, and examine clinical and genetic correlations. Based on modern concepts, non-syndromic hereditary cataracts are predominantly caused by genetic disease forms associated with mutations in crystallin and connexin genes. Therefore, a comprehensive approach to studying hereditary cataracts is necessary for early diagnosis and improved treatment outcomes. The crystallin (CRYAA, CRYAB, CRYGC, CRYGD, and CRYBA1) and connexin (GJA8, GJA3) genes were analyzed in 45 unrelated families from the Volga–Ural Region (VUR) with hereditary congenital cataracts. Pathogenic and probably pathogenic nucleotide variants were identified in ten unrelated families, nine of which had cataracts in an autosomal dominant pattern of inheritance. Two previously undescribed likely pathogenic missense variants were identified in the CRYAA gene: c.253C &gt; T (p.L85F) in one family and c.291C &gt; G (p.H97Q) in two families. The known mutation c.272_274delGAG (p.G91del) was found in the CRYBA1 gene in one family, while no pathogenic variants were found in the CRYAB, CRYGC, or CRYGD genes in the examined patients. In the GJA8 gene, the known mutation c.68G &gt; C (p.R23T) was found in two families, and previously undescribed variants were identified in two other families: a c.133_142del deletion (p.W45Sfs*72) and a missense variant, c.179G &gt; A (p.G60D). In one patient with a recessive form of cataract, two compound-heterozygous variants were identified—a previously undescribed likely pathogenic missense variant, c.143A &gt; G (p.E48G), and a known variant with uncertain pathogenetic significance, c.741T &gt; G (p.I24M). Additionally, a previously undescribed deletion, c.del1126_1139 (p.D376Qfs*69), was identified in the GJA3 gene in one family. In all families where mutations were identified, cataracts were diagnosed either immediately after birth or during the first year of life. The clinical presentation of the cataracts varied depending on the type of lens opacity, resulting in various clinical forms. This information emphasizes the importance of early diagnosis and genetic testing for hereditary congenital cataracts to guide appropriate management and improve outcomes.

Transcriptional analysis reveals that the intracellular lipid accumulation impairs gene expression profiles involved in insulin response-associated cardiac functionality

Cardiovascular disease (CVD) is a multisystemic and multicellular pathology that is generally associated with high levels of atherogenic lipoproteins in circulation. These lipoproteins tend to be retained and modified, for example, aggregated low-density lipoprotein (aggLDL), in the extracellular matrix of different tissues, such as the vascular wall and heart. The uptake of aggLDL generates a significant increase in cholesteryl ester (CE) in these tissues. We previously found that the accumulation of CE generates alterations in the insulin response in the heart. Although the insulin response is mainly associated with the uptake and metabolism of glucose, other studies have shown that insulin would fulfill functions in this tissue, such as regulating the calcium cycle and cardiac contractility. Here, we found that aggLDL induced-lipid accumulation altered the gene expression profile involved in processes essential for cardiac functionality, including insulin response and glucose uptake (Insr, Ins1, Pik3ip1, Slc2a4 gene expression), calcium cycle (Cacna1s and Gjc2 gene expression) and calcium-dependent cardiac contractility (Myh3), and cholesterol efflux (Abca1), in HL-1 cardiomyocytes. These observations were recapitulated using an in vivo model of hypercholesterolemic ApoE-KO mice. Altogether, these results may explain the deleterious effect of lipid accumulation in the myocardium, with important implications for lipid-overloaded associated CVD, including impaired insulin response, disrupted lipid metabolism, altered cardiac structure, and increased susceptibility to cardiovascular events.

Loss of the Tbx5 gene in the ventricular conduction system induces spontaneous ventricular arrhythmias

The ventricular conduction system (VCS) and the working myocardium (WM) derive from the same myogenic progenitors during the embryonic development. The VCS development is regulated by numerous genes including the T-box transcription factor 5 (Tbx5). In human, Tbx5 mutations cause Holt-Oram syndrome, an autosomal dominant disease associated with heart abnormalities such as arrhythmias. In adult mice, the deletion of the Tbx5 gene provoked a slowing of ventricular conduction due to a loss of the gap junction Connexin 40 and dysfunction of cardiac channels. However, it is still unknown how Tbx5 deletion affects the development and the function of the VCS. The aim is to study the consequences of the Tbx5 deletion in embryonic progenitors of the ventricular conduction system on cardiac function in adult mice. Conditional deletion of Tbx5 alleles in mice was induced by expressing the Cre recombinase under the control of the Connexin 40 (Cx40) gene. We studied two groups of mutants: Tbx5 deletion at embryonic days E13-14 targeting both the ventricular conduction system and the working myocardium (“VCS + WM” group; n = 40) and mice deleted at E18-P2 targeting only the ventricular conduction system (“VCS” group; n = 17). Surface ECGs were achieved monthly until 3 months of age, when immunostaining was performed on the left VCS. Immunostaining showed a reduced expression of the two major connexines in the ventricle (Cx40 and Cx43) and a reduced number of conductive cells in both mutants, suggesting a defective maturation of the VCS (Fig. 1). Furthermore, the loss of Cx43 was correlated with that of Tbx5, reflecting a direct transcriptional effect. Surface ECG revealed a significant increase of the ventricular activation duration in both mutants (P < 0.01). Moreover, premature ventricular contractions (PVCs) and a left QRS axis deviation were observed in both mutants. Finally, these PVCs disappeared with age in both mutants under resting conditions, and are unmasked when the heart is challenged with a β-1 adrenergic agonist. Our results provide new insights into Tbx5 targets in the VCS. Tbx5 deletion impacts the maturation and the anatomy of the VCS as proved by the deviation of the ventricular electrical axis, which even occurs when the VCS is already formed. Tbx5 appears to have a direct impact on the Gja1 gene, encoding the gap junction Cx43, which is reduced at the junction between the VCS and the WM in both mutants and may be responsible for PVCs.

MiRNA Profiling of Developing Rat Retina in the First Three Postnatal Weeks

The morphogenesis of the mammalian retina depends on the precise control of gene expression during development. Small non-coding RNAs, including microRNAs play profound roles in various physiological and pathological processes via gene expression regulation. A systematic analysis of the expression profile of small non-coding RNAs in developing Wistar rat retinas (postnatally day 5 (P5), P7, P10, P15 and P21) was executed using IonTorrent PGM next-generation sequencing technique to reveal the crucial players in the early postnatal retinogenesis. Our analysis reveals extensive regulatory potential of microRNAs during retinal development. We found a group of microRNAs that show constant high abundance (miR-19, miR-101; miR-181, miR-183, miR-124 and let-7) during the development process. Others are present only in the early stages (miR-20a, miR-206, miR-133, miR-466, miR-1247, miR-3582), or at later stages (miR-29, miR-96, miR-125, miR-344 or miR-664). Further miRNAs were detected which are differentially expressed in time. Finally, pathway enrichment analysis has revealed 850 predicted target genes that mainly participate in lipid-, amino acid- and glycan metabolisms in the examined time-period (P5–P21). P5–P7 transition revealed the importance of miRNAs in glutamatergic synapse and gap junction pathways. Significantly downregulated miRNAs rno-miR-30c1 and 2, rno-miR-205 and rno-miR-503 were detected to target Prkx (ENSRNOG00000003696), Adcy6 (ENSRNOG00000011587), Gnai3 (ENSRNOG00000019465) and Gja1 (ENSRNOG00000000805) genes. The dataset described here will be a valuable resource for clarifying new regulatory mechanisms for retinal development and will greatly contribute to our understanding of the divergence and function of microRNAs.

Description of Phenotypic Heterogeneity in a GJC2-Related Family and Literature Review

Introduction: Homozygous and compound heterozygous variants in GJC2, the gene encoding connexin-47 protein, cause Pelizaeus-Merzbacher-like disease type 1 or hypomyelinating leukodystrophy 2 (HLD2), a severe infantile-onset hypomyelinating leukodystrophy, and rarely some milder phenotypes like hereditary spastic paraplegia (HSP) type 44 (SPG44) and subclinical leukodystrophy. Herein, we report an Iranian GJC2-related family with intrafamilial phenotypic heterogeneity and review the literatures. Methods: Whole-exome sequencing was performed for an Iranian proband, who was initially diagnosed as HSP case. Data were analyzed and the candidate variant was confirmed by PCR and Sanger sequencing subsequently checked in family members to co-segregation analysis. A careful clinical and paraclinical evaluation of all affected individuals of the family was done and compared with previous reported GJC2-related families. Results: A novel homozygous variant, c.G14T:p.Ser5Ile, in the GJC2 gene was identified. The variant was co-segregated with the disease status in the family members. Clinical evaluation of all patients showed two distinct GJC2-related phenotypes in this family; the proband presented a complicated form of HSP, whereas both his affected sisters presented a HLD2 phenotype. Discussion: Up to now, correlation between HSP and GJC2 variants has been reported once. Here, the second case of SPG44 was identified that emphasizes on GJC2 as a HSP-causing gene. So, the screening of GJC2 in patients with HSP or HSP-like phenotypes especially with hypomyelination in their brain MRI is recommended. Also, for the first time, intrafamilial phenotypic heterogeneity for “two distinct GJC2-related phenotypes: HLD2 and HSP” was reported. Such intrafamilial phenotypic heterogeneity for GJC2 can emphasize on the shared pathophysiology of these disorders.