Zhimiao Lin

Exome sequencing reveals mutations in TRPV3 as a cause of Olmsted syndrome.

Olmsted syndrome (OS) is a rare congenital disorder characterized by palmoplantar and periorificial keratoderma, alopecia in most cases, and severe itching. The genetic basis for OS remained unidentified. Using whole-exome sequencing of case-parents trios, we have identified a de novo missense mutation in TRPV3 that produces p.Gly573Ser in an individual with OS. Nucleotide sequencing of five additional affected individuals also revealed missense mutations in TRPV3 (which produced p.Gly573Ser in three cases and p.Gly573Cys and p.Trp692Gly in one case each). Encoding a transient receptor potential vanilloid-3 cation channel, TRPV3 is primarily expressed in the skin, hair follicles, brain, and spinal cord. In transfected HEK293 cells expressing TRPV3 mutants, much larger inward currents were recorded, probably because of the constitutive opening of the mutants. These gain-of-function mutations might lead to elevated apoptosis of keratinocytes and consequent skin hyperkeratosis in the affected individuals. Our findings suggest that TRPV3 plays essential roles in skin keratinization, hair growth, and possibly itching sensation in humans and selectively targeting TRPV3 could provide therapeutic potential for keratinization or itching-related skin disorders.

Loss-of-Function Mutations in HOXC13 Cause Pure Hair and Nail Ectodermal Dysplasia

Pure hair and nail ectodermal dysplasia (PHNED) is a congenital condition characterized by hypotrichosis and nail dystrophy. Autosomal-recessive PHNED has previously been mapped to chromosomal region 12q12-q14.1, which contains the type II hair keratin and HOXC clusters. Hoxc13-null mice are known to develop hair and nail defects very similar to those seen in human PHNED. We performed whole-exome sequencing in a consanguineous Chinese family affected by PHNED and identified a homozygous nonsense mutation (c.390C>A [p.Tyr130(∗)]) in HOXC13 in all affected individuals. In an additional affected female from a consanguineous Afghan family, we found a 27.6 kb homozygous microdeletion involving the first exon of HOXC13. We examined HOXC13 expression in scalp specimen obtained from the index individual of the Chinese family and detected dramatically reduced mRNA levels in skin tissue and nearly absent protein staining in hair follicles, suggesting a mechanism of nonsense-mediated mRNA decay. We also observed markedly decreased expression of four HOXC13 target genes in the specimen. Taken together, our results demonstrate that loss-of-function mutations in HOXC13 cause autosomal-recessive PHNED and further highlight the importance of HOXC13 in hair and nail development.

DNA polymerase-α regulates the activation of type I interferons through cytosolic RNA:DNA synthesis

Aberrant nucleic acids generated during viral replication are the main trigger for antiviral immunity, and mutations that disrupt nucleic acid metabolism can lead to autoinflammatory disorders. Here we investigated the etiology of X-linked reticulate pigmentary disorder (XLPDR), a primary immunodeficiency with autoinflammatory features. We discovered that XLPDR is caused by an intronic mutation that disrupts the expression of POLA1, which encodes the catalytic subunit of DNA polymerase-α. Unexpectedly, POLA1 deficiency resulted in increased production of type I interferons. This enzyme is necessary for the synthesis of RNA:DNA primers during DNA replication and, strikingly, we found that POLA1 is also required for the synthesis of cytosolic RNA:DNA, which directly modulates interferon activation. Together this work identifies POLA1 as a critical regulator of the type I interferon response.

New and Recurrent SERPINB7 Mutations in Seven Chinese Patients with Nagashima-Type Palmoplantar Keratosis

of cardiovascular disease, we felt that these exclusion criteria were necessary to calculate the incidence of disease. Patient adherence cannot be assessed from pharmacy records. Other medications, family history, or lifestyle variables were not included in our analysis. All patients who were prescribed a tetracycline, regardless of duration, were included. It is not possible to know whether the prescription was truly given for acne/rosacea versus an infection. There are data that rosacea itself may increase the risk of cardiovascular disease (Duman et al., 2013), and it is possible that any indication for a tetracycline may perhaps positively affect the pro-inflammatory state of the rosacea patient. In private practice, the use of low-dose (20 or 40 mg daily) doxycycline is commonplace in order to take advantage of the sub-antimicrobial dose that also provides an anti-inflammatory effect in rosacea. This formulation is not available at our facility, and most patients were prescribed between 50–200 mg daily. Owing to sampling issues (three different medications in two different groups of patients, acne, and rosacea), we did not analyze the odds ratio for each of the tetracycline medications: tetracycline, doxycycline, and minocycline. Finally, as our veteran population was predominantly male, our results may not be generalizable to a more heterogeneous population. CONFLICT OF INTEREST JD has received fees from Galderma Laboratories for consulting that was performed after the design and completion of this study.

Exome sequencing reveals mutation in GJA1 as a cause of keratoderma-hypotrichosis-leukonychia totalis syndrome

Keratoderma-hypotrichosis-leukonychia totalis syndrome (KHLS) is an extremely rare, autosomal-dominant disorder characterized by severe skin hyperkeratosis, congenital alopecia and leukonychia totalis. The genetic defect underlying KHLS remained undetermined. By performing whole-exome sequencing in a family with KHLS, we identified a heterozygous mutation (c.23G>T [p.Gly8Val]) in GJA1, which cosegregated with the phenotype in the family. In an additional affected individual, we also found the identical de novo mutation which was absent in his unaffected family members. GJA1 encodes a gap junction protein connexin 43 (Cx43) which is ubiquitously expressed in various organs, including the epidermis and hair follicles. In vitro studies on HEK293 cells expressing Cx43(Gly8Val) found that the protein formed gap junction plaques between adjacent transfected cells, as observed in the wild-type. Dye-transfer experiments by microinjection of Lucifer yellow displayed functional gap junction of the Cx43(Gly8Val) mutant. Using patch clamp and Ca(2+) imaging methods, we observed that the Cx43(Gly8Val) hemichannel had significantly more openings than Cx43(WT), facilitating Ca(2+) influx at resting potential. Such gain-of-function effect might result in cytoplasmic Ca(2+) overload, accelerated apoptosis of keratinocytes and subsequent skin hyperkeratosis. Taken together, our results demonstrated that, with probably enhanced hemichannel activities, a mutation in GJA1 is linked to KHLS without extracutaneous involvement.

New mutations in the transglutaminase 1 gene in three families with lamellar ichthyosis

Background.  Autosomal recessive lamellar ichthyosis (LI) is a severe skin disorder characterized by generalized hyperkeratosis. Gene mutation in transglutaminase 1 (TGM1), which mediates cross‐links in the formation of the cell envelope during terminal differentiation of epidermis, has been identified as a cause of LI.

Mutation hotspots of SCN9A in primary erythermalgia.

naevus, we performed immunohistochemical staining with the antiandrogen receptor monoclonal antibody MU256-UC (BioGenex, San Ramon, CA, U.S.A.), which revealed strong androgen receptor immunoreactivity to the nuclei of epidermal keratinocytes, compared with normal skin (data not shown). The two distinct anomalies might originate from one common postzygotic mutation arising during the initial stage of embryonic development. In summary, we report a case of hypohidrosis confined within a Becker’s naevus lesion, and consider the possibility of postzygotic mutation of a common genetic locus. In the Becker’s naevus, the specific relationship linking the gene involved and the developmental fields are far from clear, and therefore additional investigations at the molecular genetic level are needed.

Identification of LCK mutation in a family with atypical epidermodysplasia verruciformis with T-cell defects and virus-induced squamous cell carcinoma.

Inherited epidermodysplasia verruciformis (EV) is a rare skin disorder characterized by susceptibility to specific types of human papilloma virus (HPV) and is strongly associated with skin carcinomas. Inactivating mutations in EVER1/EVER2 account for most cases of EV. However, more phenotypes related to but distinct from EV have been reported with an immunodeficiency state but without EVER1/EVER2 mutation, and the genetic basis for these atypical EV cases is poorly understood.

Recurrent splice-site mutation in MBTPS2 underlying IFAP syndrome with Olmsted syndrome-like features in a Chinese patient

Mutations in MBTPS2 have been reported to cause a broad phenotypic spectrum of X‐linked genodermatoses, including IFAP (ichthyosis follicularis; atrichia and photophobia) syndrome (OMIM 308205) with or without BRESHECK (brain anomalies, retardation of mentality and growth, ectodermal dysplasia, skeletal malformations, Hirschsprung disease, ear deformity and deafness, eye hypoplasia, cleft palate, cryptorchidism, and kidney dysplasia/hypoplasia) syndrome, keratosis follicularis spinulosa decalvans (KFSD; OMIM 308800) and an X‐linked form of Olmsted syndrome. We report a recurrent intronic mutation in MBTPS2 (c.671‐9T>G) in a Chinese patient with the typical triad of IFAP syndrome (i.e. ichthyosis, atrichia and photophobia), along with pachyonychia, palmoplantar and periorificial keratoderma, which were reminiscent of Olmsted syndrome. Interestingly, this mutation was previously reported in two cases of IFAP without keratoderma, which suggests clinical heterogeneicity of the same mutation in MBTPS2. The concomitance of Olmsted syndrome‐like features in this patient with IFAP may challenge the existence of the X‐linked form of Olmsted syndrome as an independent condition.

Loss-of-Function Mutations in CAST Cause Peeling Skin, Leukonychia, Acral Punctate Keratoses, Cheilitis, and Knuckle Pads

Calpastatin is an endogenous specific inhibitor of calpain, a calcium-dependent cysteine protease. Here we show that loss-of-function mutations in calpastatin (CAST) are the genetic causes of an autosomal-recessive condition characterized by generalized peeling skin, leukonychia, acral punctate keratoses, cheilitis, and knuckle pads, which we propose to be given the acronym PLACK syndrome. In affected individuals with PLACK syndrome from three families of different ethnicities, we identified homozygous mutations (c.607dup, c.424A>T, and c.1750delG) in CAST, all of which were predicted to encode truncated proteins (p.Ile203Asnfs∗8, p.Lys142∗, and p.Val584Trpfs∗37). Immunohistochemistry shows that staining of calpastatin is reduced in skin from affected individuals. Transmission electron microscopy revealed widening of intercellular spaces with chromatin condensation and margination in the upper stratum spinosum in lesional skin, suggesting impaired intercellular adhesion as well as keratinocyte apoptosis. A significant increase of apoptotic keratinocytes was also observed in TUNEL assays. In vitro studies utilizing siRNA-mediated CAST knockdown revealed a role for calpastatin in keratinocyte adhesion. In summary, we describe PLACK syndrome, as a clinical entity of defective epidermal adhesion, caused by loss-of-function mutations in CAST.