A recurrent mutation of GJB6 in a big Chinese family with Hidrotic ectodermal dysplasia

Botanical extract combined with minoxidil improve hidrotic ectodermal dysplasia caused by p.G11R mutations: a case report

PURPOSE

We aim to explore a potential treatment strategy for hair loss.

MATERIALS AND METHODS

A male 6-year-old child was diagnosed with hidrotic ectodermal dysplasia 2 (HED2) caused by GJB6 (p.G11R) mutations. He presented at our clinic with diffuse thinning and fine and brittle hair since birth. Additionally, the child exhibited abnormal development of teeth, fingernails, and toenails. The condition of the child's hair had not improved significantly with age. He was treated with botanical extracts combined with Minoxidil.

RESULTS

After one and a half months of treatment, the patient showed remarkable hair growth.

CONCLUSIONS

Our team has previously used botanical extracts in combination for the treatment of autosomal recessive wooly hair in children. In the present case, treatment with botanical extract combined with minoxidil was found to be equally efficacious. This case report provides valuable information for future studies on the use of botanical extracts in treating hair loss, as well as a safe and effective potential treatment strategy for children with congenital alopecia.

Exploring the evidence for mitochondrial dysfunction and genetic abnormalities in the etiopathogenesis of tropical ataxic neuropathy

Tropical ataxic neuropathy (TAN) is characterised by ataxic polyneuropathy, degeneration of the posterior columns and pyramidal tracts, optic atrophy, and sensorineural hearing loss. It has been attributed to nutritional/toxic etiologies, but evidence for the same has been equivocal. TAN shares common clinical features with inherited neuropathies and mitochondrial disorders, it may be hypothesised that genetic abnormalities may underlie the pathophysiology of TAN. This study aimed to establish evidence for mitochondrial dysfunction by adopting an integrated biochemical and multipronged genetic analysis. Patients (n = 65) with chronic progressive ataxic neuropathy with involvement of visual and/or auditory pathways underwent deep phenotyping, genetic studies including mitochondrial DNA (mtDNA) deletion analysis, mtDNA and clinical exome sequencing (CES), and respiratory chain complex (RCC) assay. The phenotypic characteristics included dysfunction of visual (n = 14), auditory (n = 12) and visual + auditory pathways (n = 29). Reduced RCC activity was present in 13 patients. Mitochondrial DNA deletions were noted in five patients. Sequencing of mtDNA (n = 45) identified a homoplasmic variant (MT-ND6) and a heteroplasmic variant (MT-COI) in one patient each. CES (n = 45) revealed 55 variants in nuclear genes that are associated with neuropathy (n = 27), deafness (n = 7), ataxia (n = 4), and mitochondrial phenotypes (n = 5) in 36 patients. This study provides preliminary evidence that TAN is associated with a spectrum of genetic abnormalities, including those associated with mitochondrial dysfunction, which is in contradistinction from the prevailing hypothesis that TAN is related to dietary toxins. Analysing the functional relevance of these genetic variants may improve the understanding of the pathogenesis of TAN.

A novel variant in the GJB6 gene in a large Chinese family with a unique phenotype of Clouston syndrome

Clouston syndrome (OMIM #129500), also known as hidrotic ectodermal dysplasia type 2, is a rare autosomal dominant skin disorder. To date, four mutations in the GJB6 gene, G11R, V37E, A88V, and D50N, have been confirmed to cause this condition. In previous studies, the focus has been mainly on gene sequencing, and there has been a lack of research on clinical manifestations and pathogenesis. To confirm the diagnosis of this pedigree at the molecular level and summarize and analyse the clinical phenotype of patients and to provide a basis for further study of the pathogenesis of the disease, we performed whole-exome and Sanger sequencing on a large Chinese Clouston syndrome pedigree. Detailed clinical examination included histopathology, hair microscopy, and scanning electron microscopy. We found a novel heterozygous missense variant (c.134G>C:p.G45A) for Clouston syndrome. We identified a new clinical phenotype involving all nail needling pain in all patients and found a special honeycomb hole structure in the patients' hair under scanning electron microscopy. Our data reveal that a novel variant (c.134G>C:p.G45A) plays a likely pathogenic role in this pedigree and highlight that genetic testing is necessary for the diagnosis of Clouston syndrome.

Hidrotic ectodermal dysplasia in a Chinese pedigree: A case report

BACKGROUND

We report on a large family of Chinese Han individuals with hidrotic ectodermal dysplasia (HED) with a variation in GJB6 (c.31G>A). The patients in the family had a triad of clinical manifestations of varying degrees. Although the same variation locus have been reported, the clinical manifestations of this family were difficult to distinguish from those of congenital thick nail disorder, palmoplantar keratosis, and congenital hypotrichosis.

CASE SUMMARY

This investigation involved a large Chinese family of 46 members across five generations and included 12 patients with HED. The proband (IV4) was a male patient with normal sweat gland function and dental development, no skeletal dysplasia, no cognitive disability, and no hearing impairments. His parents were not consanguineously married. Physical examination of the proband revealed thinning hair and thickened grayish-yellow nails and toenails with some longitudinal ridges, in addition to mild bilateral palmoplantar hyperkeratosis. GJB6, GJB2, and GJA1 have been reported to be the causative genes of HED; therefore, we subjected the patient’s samples to Sanger sequencing of these three genes. In this family, the variation locus was at GJB6 (c.31G>A, p.Gly11Arg). Overexpression vectors of wild-type GJB6 and its variants were established and transfected into HaCaT cell models, and the related mRNA and protein expression changes were determined using real-time reverse transcriptase-polymerase chain reaction and Western blot, respectively.

CONCLUSION

We report another HED phenotype associated with GJB6 variations, which can help clinicians to diagnose HED despite its varying presentations.

Mutant Cx30-A88V mice exhibit hydrocephaly and sex-dependent behavioral abnormalities, implicating a functional role for Cx30 in the brain

Connexin 30 (Cx30; also known as Gjb6 when referring to the mouse gene) is expressed in ependymal cells of the brain ventricles, in leptomeningeal cells and in astrocytes rich in connexin 43 (Cx43), leading us to question whether patients harboring GJB6 mutations exhibit any brain anomalies. Here, we used mice harboring the human disease-associated A88V Cx30 mutation to address this gap in knowledge. Brain Cx30 levels were lower in male and female Cx30^A88V/A88V mice compared with Cx30^A88V/+ and Cx30^+/+ mice, whereas Cx43 levels were lower only in female Cx30 mutant mice. Characterization of brain morphology revealed a disrupted ependymal cell layer, significant hydrocephalus and enlarged ventricles in 3- to 6-month-old adult male and female Cx30^A88V/A88V mice compared with Cx30^A88V/+ or Cx30^+/+ sex-matched littermate mice. To determine the functional significance of these molecular and morphological changes, we investigated a number of behavioral activities in these mice. Interestingly, only female Cx30^A88V/A88V mice exhibited abnormal behavior compared with all other groups. Cx30^A88V/A88V female mice demonstrated increased locomotor and exploratory activity in both the open field and the elevated plus maze. They also exhibited dramatically reduced ability to learn the location of the escape platform during Morris water maze training, although they were able to swim as well as other genotypes. Our findings suggest that the homozygous A88V mutation in Cx30 causes major morphological changes in the brain of aging mice, possibly attributable to an abnormal ependymal cell layer. Remarkably, these changes had a more pronounced consequence for cognitive function in female mice, which is likely to be linked to the dysregulation of both Cx30 and Cx43 levels in the brain.

Harnessing the therapeutic potential of antibodies targeting connexin hemichannels

BACKGROUND

Connexin hemichannels have been implicated in pathology-promoting conditions, including inflammation, numerous widespread human diseases, including cancer and diabetes, and several rare diseases linked to pathological point mutations.

METHODS

We analysed the literature focusing on antibodies capable of modulating hemichannel function, highlighting generation methods, applications to basic biomedical research and translational potential.

RESULTS

Anti-hemichannel antibodies generated over the past 3 decades targeted mostly connexin 43, with a focus on cancer treatment. A slow transition from relatively unselective polyclonal antibodies to more selective monoclonal antibodies resulted in few products with interesting characteristics that are under evaluation for clinical trials. Selection of antibodies from combinatorial phage-display libraries, has permitted to engineer a monoclonal antibody that binds to and blocks pathological hemichannels formed by connexin 26, 30 and 32.

CONCLUSIONS

All known antibodies that modulate connexin hemichannels target the two small extracellular loops of the connexin proteins. The extracellular region of different connexins is highly conserved, and few residues of each connexins are exposed. The search for new antibodies may develop an unprecedented potential for therapeutic applications, as it may benefit tremendously from novel whole-cell screening platforms that permit in situ selection of antibodies against membrane proteins in native state. The demonstrated efficacy of mAbs in reaching and modulating hemichannels in vivo, together with their relative specificity for connexins overlapping epitopes, should hopefully stimulate an interest for widening the scope of anti-hemichannel antibodies. There is no shortage of currently incurable diseases for which therapeutic intervention may benefit from anti-hemichannel antibodies capable of modulating hemichannel function selectively and specifically.