Loss-of-function variants in GLMN are associated with generalized skin hyperpigmentation with or without glomuvenous malformation.

BACKGROUND: Inherited hyperpigmented skin disorders comprise a group of entities with considerable clinical and genetic heterogenicity. The genetic basis of a majority of these disorders remains to be elucidated. OBJECTIVES: This study aimed to identify the underlying gene for an unclarified disorder of autosomal-dominant generalized skin hyperpigmentation with or without glomuvenous malformation. METHODS: Whole-exome sequencing was performed in five unrelated families with autosomal-dominant generalized skin hyperpigmentation. Variants were confirmed using Sanger sequencing and a minigene assay was employed to evaluate the splicing alteration. Immunofluorescence and transmission electron microscopy (TEM) were used to determine the quantity of melanocytes and melanosomes in hyperpigmented skin lesions. GLMN knockdown by small interfering RNA assays was performed in human MNT-1 cells to examine melanin concentration and the underlying molecular mechanism. RESULTS: We identified five variants in GLMN in five unrelated families, including c.995_996insAACA(p.Ser333Thrfs*11), c.632 + 4delA, c.1470_1473dup(p.Thr492fs*12), c.1319G > A(p.Trp440*) and c.1613_1614insTA(Thr540*). The minigene assay confirmed that the c.632 + 4delA mutant resulted in abolishment of the canonical donor splice site. Although the number of melanocytes remained unchanged in skin lesions, as demonstrated by immunofluorescent staining of tyrosinase and premelanosome protein, TEM revealed an increased number of melanosomes in the skin lesion of a patient. The GLMN knockdown MNT-1 cells demonstrated a higher melanin concentration, a higher proportion of stage III and IV melanosomes, upregulation of microphthalmia-associated transcription factor and tyrosinase, and downregulation of phosphorylated p70S6 K vs. mock-transfected cells. CONCLUSIONS: We found that loss-of-function variants in GLMN are associated with generalized skin hyperpigmentation with or without glomuvenous malformation. Our study implicates a potential role of glomulin in human skin melanogenesis, in addition to vascular morphogenesis.

A group of skin conditions known as 'inherited hyperpigmented skin disorders' includes some diseases with different clinical and genetic traits. The genetic basis of the majority of these diseases is not understood. To identify the gene responsible for a disease that causes darker patches of skin (hyperpigmentation) with or without the abnormal growth of blood vessels and the presence of cells named glomus cells (a glomuvenous malformation), we used genetic techniques called whole-exome sequencing and Sanger sequencing in five unrelated families with this disease. We also used a technique called a 'minigene assay' to evaluate genetic alterations in a gene called GLMN, which encodes a protein called glomulin. Immunofluorescence and transmission electron microscopy (TEM) were used to determine the number of pigment-producing cells (called melanocytes) and melanosomes (where the pigment melanin is synthesized, stored and transported) in hyperpigmented skin lesions. We identified five different variants of the GLMN gene in five unrelated families. Although the number of melanocytes remained unchanged in skin lesions, TEM revealed an increased number of melanosomes. By 'switching off' the GLMN gene, we found that skin cells produced more pigment, as well as the proteins MITF and tyrosinase; they also showed a decrease in the phosphorylated protein p-p70S6 K. Overall, we found that loss-of-function mutations in GLMN caused skin hyperpigmentation with or without abnormal blood vessels. The results suggest there could be a potential role of the protein glomulin in human skin colour and blood vessel changes.

A gain-of-function variant in SREBF1 causes generalized skin hyperpigmentation with congenital cataracts.

BACKGROUND: Lipid metabolism has essential roles in skin barrier formation and the regulation of skin inflammation. Lipid homeostasis regulates skin melanogenesis, although the underlying mechanism remains largely unknown. Sterol regulatory element binding protein 1 (SREBP-1) is a key transcription factor essential for cellular lipid metabolism. Loss-of-function variants in SREBF1 are responsible for autosomal-dominant ichthyosis follicularis, alopecia and photophobia syndrome, emphasizing the significance of lipid homeostasis in skin keratinization. OBJECTIVES: To identify the genetic basis of a new entity featuring diffuse skin hyperpigmentation with congenital cataracts, and to unravel the underlying mechanism for the pathogenesis of the SREBF1 variant. METHODS: Whole-exome sequencing was performed to identify underlying genetic variants. Quantitative polymerase chain reaction, Western blot and immunofluorescence staining were used to assess the expression and the subcellular localization of the SREBF1 variant. The transcriptional activity of mutant SREBP-1 was determined by a luciferase reporter assay. A transgenic zebrafish model was constructed. RESULTS: Two unrelated patients presented with generalized skin hyperpigmentation with skin xerosis, congenital cataracts and extracutaneous symptoms. We identified a de novo nonsense variant c.1289C>A (p.Ser430*) in SREBF1 in both patients. The variant encoded a truncated protein that showed preferential nucleus localization, in contrast to wild-type SREBP-1 which - in sterol-sufficient conditions - is mainly localized in the cytoplasm. The luciferase reporter assay revealed that the p.Ser430* mutant exhibited enhanced transcriptional activity. Cultured patient primary melanocytes showed increased melanin synthesis vs. those from healthy controls. At 35 days postfertilization, the p.Ser430* transgenic zebrafish model exhibited more black spots, along with upregulated expression of melanogenic genes. CONCLUSIONS: We demonstrated that a gain-of-function variant of SREBF1 causes a previously undescribed disorder characterized by generalized skin hyperpigmentation and congenital cataracts. Our study reveals the involvement of SREBP-1 in melanogenesis and lens development, and paves the way for the development of novel therapeutic targets for skin dyspigmentation or cataracts.

The genetic basis of many diseases that cause skin hyperpigmentation are not fully understood. Hyperpigmentation means that some patches of skin are darker than others. This is caused by the overproduction of a pigment called melanin. We report on two patients who were born with skin hyperpigmentation and cataracts. The cause of the patients' disease was unknown, so we carried out genetic testing in the patients. The tests showed that both patients had a change ('mutation') in a gene called 'SREBF1'. This gene encodes for a protein called SREBF-1. Other mutations in this protein are involved in other skin diseases. A different test showed that the mutated SREBF1 gene was activated more often than normal. Skin cells taken from both patients also produced more pigment than cells taken from people without hyperpigmentation. To confirm this gene mutation causes more skin pigmentation, we did an experiment with zebrafish with the same mutation. At 35 days after fertilization, the zebrafish showed more black spots on their skin. Our study reveals the involvement of SREBP-1 in the production of melanin and lens development in the eye. The findings may offer a new approach to treating hyperpigmentation in skin diseases.

Variants in KLK11, affecting signal peptide cleavage of kallikrein-related peptidase 11, cause an autosomal-dominant cornification disorder.

BACKGROUND: Mendelian disorders of cornification (MeDOC) are a group of heterogeneous genodermatoses with different genetic bases. The pathogenesis of a substantial group of MeDOC remains to be elucidated. OBJECTIVES: To identify a new causative gene and the pathogenesis of a previously undescribed autosomal-dominant cornification disorder. METHODS: Whole-exome sequencing was performed in three families with the novel cornification disorder to identify the disease-causing variants. As the variants were located around the signal peptide (SP) cleavage site of a kallikrein-related peptidase, SP cleavage, subcellular localization and extracellular secretion of the variants were evaluated in eukaryotic overexpression systems by Western blotting or immunocytochemistry. Then the trypsin-like and chymotrypsin-like proteolytic activity of the peptidase and degradation of its catalytic substrate were assayed using the patients' stratum corneum (SC) samples. The morphology of the lamellar bodies and corneodesmosomes (CDs) in the patients' SC was ultrastructurally examined. A mouse model harbouring the equivalent variant was constructed and evaluated histologically. RESULTS: We identified two heterozygous variants affecting Gly50 in kallikrein-related peptidase (KLK)11 in a familial case and two sporadic cases with the new disorder, which is characterized by early-onset ichthyosiform erythroderma or erythrokeratoderma. KLK11 belongs to the family of kallikrein-related peptidases participating in skin desquamation by decomposing CDs, a process essential for shedding of the SC. In vitro experiments demonstrated that the variants perturbed the SP cleavage of KLK11, leading to subcellular mislocalization and impaired extracellular secretion of the KLK11 Gly50Glu variant. Both trypsin-like and chymotrypsin-like proteolytic activities were significantly decreased in the patients' SC samples. Reduced proteolysis of desmoglein 1 and delayed degeneration of CDs were detected in patients' SC, indicating delayed skin desquamation. Consistently, the patients showed a thickened, dense SC, indicating abnormal skin desquamation. Mice harbouring the homozygous c.131G>A (p.Gly44Glu) Klk11 variant, which is equivalent to KLK11 c.149G>A (p.Gly50Glu) in humans, exhibited hyperkeratosis and abnormal desquamation, partially recapitulating the phenotype. CONCLUSIONS: We provide evidence that variants at Gly50 affecting the SP cleavage of KLK11 cause a new autosomal-dominant cornification disorder with abnormal desquamation. Our findings highlight the essential role of KLKs in maintaining homeostasis of skin keratinization and desquamation.

Dermatopathological features and successful treatment with topical antioxidant for ichthyosiform lesions in Mitchell syndrome caused by an ACOX1 variant.

Peroxisomal acyl-CoA oxidase 1 (ACOX1), is a peroxisomal enzyme that catalyzes ß-oxidation of very-long-chain fatty acids (VLCFA). The gain-of-function variant p.Asn237Ser in ACOX1 has been shown to cause Mitchell syndrome (MITCH), a neurodegenerative disorder characterized by episodic demyelination, hearing loss, and polyneuropathy, through the overproduction of hydrogen peroxide. Only eight cases of MITCH have been reported. While all these patients experienced cutaneous abnormalities, detailed skin features and potential treatment have not been documented. Herein, we report two MITCH patients who harbored a de novo heterozygous variant p.Asn237Ser in ACOX1 and experienced progressive ichthyosiform erythroderma. Skin histopathology revealed hyperkeratosis and parakeratosis with focal hypogranulosis as well as dyskeratotic keratinocytes. Lipid accumulation in the epidermis was observed using Oil Red O staining. Both patients exhibited a remarkable response to treatment with the topical antioxidant N-acetylcysteine (NAC), with Patient 1 achieving complete recovery after 3 months of consistent treatment. This study provides the first comprehensive description of the clinicopathological characteristics and effective treatment of skin lesions in MITCH patients. The successful treatment with topical NAC suggests excessive reactive oxygen species might play a significant role in the pathogenesis of skin lesions in MITCH.

Unilateral focal palmoplantar keratoderma associated with a postzygotic variant in PIK3CA and activation of the PI3K/AKT/mTOR pathway.

Palmoplantar keratoderma (PPK) is a group of -disorders with genetic and phenotypic heterogeneity featuring skin thickening of the palms and soles. More than 60 genes involved in various biological processes are implicated in PPK. PIK3CA is an oncogene encoding p110α, and its somatic variants contribute to a spectrum of congenital overgrowth disorders, including epidermal nevi (EN). To identify the genetic basis and elucidate the pathogenesis of a patient with unilateral focal PPK. Whole-exome sequencing and Sanger sequencing combined with laser capture microdissection (LCM) were performed on genomic DNA extracted from the patient's peripheral blood and skin lesion. Skin biopsies were taken from the lesion of the patient and normal controls for immunofluorescence. Molecular docking was performed using Alphafold2-multimer. A three-year-old girl presented with unilateral focal PPK with an identified missense -variant (c.3140A>G, p.His1047Arg) in PIK3CA from affected tissue. This variant only existed in the lesional epidermis. Elevated PI3K/AKT/mTOR signalling in the affected epidermis and an increased number of Ki67-positive keratinocytes were demonstrated. Molecular docking indicated instability of the p110α-p85α dimer caused by the PIK3CA His1047Arg variant. We describe the first PPK case associated with a variant in PIK3CA, which expands the spectrum of PIK3CA-related disorders. Our study further underscores the importance of the PI3K/AKT/mTOR pathway in the homeostasis of skin keratinization.

Investigation of Nagashima-type palmoplantar keratoderma in China: A cross-sectional study of 234 patients.

Nagashima-type palmoplantar keratoderma (NPPK) is the most prevalent hereditary palmoplantar keratoderma (PPK) in China, but there is a paucity of epidemiological data on the Chinese population. To explore the clinical and genetic characteristics, evaluate the demographic distribution, and estimate the burden of disease of NPPK. A total of 234 Chinese patients with NPPK were enrolled from two medical centers and an online PPK support group. Next-generation sequencing and Sanger sequencing were performed to screen out and confirm pathogenic mutations in SERPINB7. Clinical features and quality of life (QOL) were evaluated using self-completed questionnaires. In total, 14 pathogenic mutations were identified in SERPINB7 from the cohort. The top four recurrent mutations were c.796C>T (355, 75.9%), c.522dupT (66, 14.1%), c.650_653delCTGT (24, 5.1%), and c.455G>T (12, 2.6%), accounting for 97.6% of Chinese NPPK patients. Other mutations (11, 2.4%) include c.455-1G>T, c.336+2T>G, c.635delG and seven novel mutations c.2T>C, c.434delG, c.455-16A>G, c.656T>C, c.745-553T>G, c.832C>T, c.1036G>T. The estimated prevalence of NPPK in China was found to be 0.975/10 000 based on Chinese databases. Clinically, there were no apparent genotype-phenotype correlations in NPPK patients. Pediatric patients mainly presented with palmoplantar peeling, while adults presented with scale (p < 0.001). The most common comorbidities in NPPK patients were onychomycosis (40.0%), eczema (36.8%), and tinea pedis (30.3%). As for burden of disease, NPPK patients' QOL was decreased by a moderate degree. In this study, pathogenic mutations' allele frequencies in SERPINB7 were updated, and prevalence of NPPK in China was estimated. This large-scale cohort study provides evidence-based recommendations for patient management. Identification of new mutations are important for timely diagnosis of NPPK. Palmoplantar peeling in children can be used as a hallmark for early recognition of NPPK.

FEN1 gene variants confer reduced risk of breast cancer in chinese women: A case-control study.

This study aimed to assess the associations of two common Flap endonuclease 1 (FEN1) polymorphisms (rs4246215 and rs174538) with breast cancer risk in northwest Chinese women. We conducted a case-control study with 560 breast cancer patients and 583 age-matched healthy controls from Northwest China. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to estimate the associations. We found a significantly reduced risk of breast cancer associated with T allele of rs4246215 (allele model: OR 0.81, 95% CI 0.68-0.96; homozygote model: OR = 0.59, 95% CI = 0.40-0.87; recessive model: OR = 0.61, 95% CI = 0.42-0.89), especially in postmenopausal women (OR = 0.58, 95% CI = 0.35-0.97). Furthermore, the polymorphism showed a decreased association with larger tumor size (heterozygote model: OR = 0.63, 95% CI = 0.44-0.92; dominant model: OR = 0.63, 95% CI = 0.44-0.90). For rs174538, we did not find any difference in all genetic models. However, rs174538 was associated with lymph node metastasis (heterozygote model: OR = 0.57, 95% CI = 0.39-0.81; dominant model: OR = 0.61, 95% CI = 0.43-0.86) and estrogen receptor status (heterozygote model: OR = 1.50, 95% CI = 1.05-2.15; dominant model: OR = 1.42, 95% CI = 1.01-1.98). Haplotype analysis showed that Trs4246215Grs174538 haplotype was a protective factor of breast cancer (OR = 0.34, 95% CI = 0.14-0.81). Our results suggest that FEN1 polymorphisms may reduce the risk of breast cancer in Chinese women.

Association of transcription factor 7-like 2 gene polymorphisms with breast cancer risk in northwest Chinese women.

Genetic variations in transcription factor 7-like 2 (TCF7L2) are associated with cancer risk. This study was conducted to establish the relationship between TCF7L2 polymorphisms (rs1225404, rs7003146, and rs7903146) and clinical features and risk of breast cancer in Northwest Chinese Han women. In this study, three polymorphisms of TCF7L2 (rs1225404, rs7003146, and rs7903146) were genotyped in 458 patients with breast cancer and 500 healthy controls using the Sequenom MassARRAY-iPLEX system. We evaluated the associations between the polymorphisms and breast cancer using odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs). The C allele of rs1225404 was associated with increased breast cancer risk (OR = 1.58, P = 0.0004, PC= 0.0012), whereas the G allele of rs7003146 was associated with decreased breast cancer risk (OR = 0.71, P = 0.01, PC= 0.03). Furthermore, the rs1225404 polymorphism positively correlated with negative progesterone receptor status. A positive correlation with positive estrogen receptor (ER) status was observed for the rs7003146 polymorphism. Our results suggest that TCF7L2 polymorphisms rs1225404 and rs7003146, but not rs7903146, may affect breast cancer risk in Northwest Chinese women. Additionally, the tag polymorphisms in TCF7L2 are associated with the clinical features of breast cancer, which may provide us novel insight into the pathogenesis of breast cancer.