Harlequin ichthyosis (HI) is the most severe and frequently lethal form of recessive congenital ichthyosis. Although defects in lipid transport, protein phosphatase activity, and differentiation have been described, the genetic basis underlying the clinical and cellular phenotypes of HI has yet to be determined. By use of single-nucleotide-polymorphism chip technology and homozygosity mapping, a common region of homozygosity was observed in five patients with HI in the chromosomal region 2q35. Sequencing of the ABCA12 gene, which maps within the minimal region defined by homozygosity mapping, revealed disease-associated mutations, including large intragenic deletions and frameshift deletions in 11 of the 12 screened individuals with HI. Since HI epidermis displays abnormal lamellar granule formation, ABCA12 may play a critical role in the formation of lamellar granules and the discharge of lipids into the intercellular spaces, which would explain the epidermal barrier defect seen in this disorder. This finding paves the way for early prenatal diagnosis. In addition, functional studies of ABCA12 will lead to a better understanding of epidermal differentiation and barrier formation.

Marie Unna hereditary hypotrichosis (MUHH) is an autosomal dominant form of genetic hair loss. In a large Chinese family carrying MUHH, we identified a pathogenic initiation codon mutation in U2HR, an inhibitory upstream ORF in the 5' UTR of the gene encoding the human hairless homolog (HR). U2HR is predicted to encode a 34-amino acid peptide that is highly conserved among mammals. In 18 more families from different ancestral groups, we identified a range of defects in U2HR, including loss of initiation, delayed termination codon and nonsense and missense mutations. Functional analysis showed that these classes of mutations all resulted in increased translation of the main HR physiological ORF. Our results establish the link between MUHH and U2HR, show that fine-tuning of HR protein levels is important in control of hair growth, and identify a potential mechanism for preventing hair loss or promoting hair removal.

Distinct germline mutations in the gene (GJB3) encoding connexin 31 (Cx31) underlie the skin disease erythrokeratoderma variabilis (EKV) or sensorineural hearing loss with/without peripheral neuropathy. Here we describe a number of functional analyses to investigate the effect of these different disease-associated Cx31 mutants on connexon trafficking and intercellular communication. Immunostaining of a biopsy taken from an EKV patient harbouring the R42P mutation revealed sparse epidermal staining of Cx31, and, when present, it had a perinuclear localization. Transfection and microinjection studies in both keratinocytes and fibroblast cell lines also demonstrated that R42P and four other EKV-associated mutant Cx31 proteins displayed defective trafficking to the plasma membrane. The deafness/neuropathy only mutant 66delD had primarily a cytoplasmic localization, but some protein was visualized at the plasma membrane in a few transfected cells. Both 66delD- and R32W-Cx31/EGFP proteins had significantly impaired dye transfer rates compared to wild-type Cx31/EGFP protein. A striking characteristic feature observed with the dominant skin disease Cx31 mutations was a high incidence of cell death. This was not observed with wild-type, R32W 66delD Cx31 proteins. In conclusion, we have identified some key cellular phenotypic differences with respect to disease-associated Cx31 mutations.

Introduction Cardiomyopathy is a common cause of morbidity and death in patients with Duchenne muscular dystrophy (DMD). Methods A cross-sectional analysis of clinical data from a multi-institutional, international CINRG DMD Natural History Study of 340 DMD patients aged 2 to 28 years. Cardiomyopathy was defined as shortening fraction (SF) <28% or ejection fraction (EF) <55%. Results 231 participants reported a prior clinical echocardiogram study, and 174 had data for SF or EF. The prevalence of cardiomyopathy was 27% (47/174), and it was significantly associated with age and clinical stage. The association of cardiomyopathy with age and clinical stage was not changed by glucocorticoid use as a covariate (P>0.68). In patients with cardiomyopathy, 57 % (27/47) reported not taking any cardiac medications. Cardiac medications were used in 12% (15/127) of patients without cardiomyopathy. Discussion Echocardiograms were underutilized, and cardiomyopathy was undertreated in this DMD natural history cohort.

To assess the clinical outcomes of 45 cases of harlequin ichthyosis and review the underlying ABCA12 gene mutations in these patients.