Trichothiodystrophy-associated MPLKIP maintains DBR1 levels for proper lariat debranching and ectodermal differentiation

The brittle hair syndrome Trichothiodystrophy (TTD) is characterized by variable clinical features, including photosensitivity, ichthyosis, growth retardation, microcephaly, intellectual disability, hypogonadism, and anaemia. TTD-associated mutations typically cause unstable mutant proteins involved in various steps of gene expression, severely reducing steady-state mutant protein levels. However, to date, no such link to instability of gene-expression factors for TTD-associated mutations in MPLKIP/TTDN1 has been established. Here, we present seven additional TTD individuals with MPLKIP mutations from five consanguineous families, with a newly identified MPLKIP variant in one family. By mass spectrometry-based interaction proteomics, we demonstrate that MPLKIP interacts with core splicing factors and the lariat debranching protein DBR1. MPLKIP-deficient primary fibroblasts have reduced steady-state DBR1 protein levels. Using Human Skin Equivalents (HSEs), we observed impaired keratinocyte differentiation associated with compromised splicing and eventually, an imbalanced proteome affecting skin development and, interestingly, also the immune system. Our data show that MPLKIP, through its DBR1 stabilizing role, is implicated in mRNA splicing, which is of particular importance in highly differentiated tissue.</p

CADASIL syndrome in a large Turkish kindred caused by the R90C mutation in the Notch3 receptor

Mutations in the Notch3 gene are the cause of the autosomal dominant disorder CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). The CADASIL is an adult-onset neurologic disorder (average age of onset is 45 years) characterized by recurrent strokes and dementia. Clinical features combined with cerebral magnetic resonance imaging (MRI), showing a diffuse leukoencephalopathy with subcortical infarcts in the basal ganglia and white matter, are highly contributive to the diagnosis. We present a Turkish family with CADASIL, in which 12 individuals in four generations were affected showing the typical clinical features of recurrent strokes. Mutation analysis of the Notch3 receptor gene identified the recently described R90C mutation in the N-terminal part of the gene in affected individuals. Interestingly, migraine without aura was found as an initial symptom of the disease in two young mutation carriers (22 and 25 years, respectively), who did not show any additional clinical features or any MRI abnormalities. This indicates that migraine without aura in the absence of MRI abnormalities may represent an early initial symptom of CADASIL, which is difficult to diagnose in the absence of molecular diagnosis. Therefore, the used molecular screening method for Notch3 mutations provides a rapid and accurate diagnostic tool in addition to the standard diagnostic procedures

[Family history, clinical features, and molecular characterization of a patient with autosomal recessive non-syndromic hearing loss].

Autosomal recessive non-syndromic hearing loss is the most common form of inherited childhood deafness. Identification of the responsible gene in this type of hearing loss presents difficulties because of marked genetic heterogenicity and limited clinical presentation. A two-year-old girl was referred to our clinic because of congenital hearing loss. Family history showed that her brother and six relatives of her parents were also affected by unilateral or bilateral hearing loss. There was no consanguinity between the parents, though they were from close villages. Audiometric studies revealed severe bilateral sensorineural hearing loss. Molecular analysis of the index patient documented that autosomal recessive non-syndromic hearing loss resulted from the homozygous 35delG mutation in the connexin 26 gene

PITFALLS OF MAPPING A LARGE TURKISH CONSANGUINEOUS FAMILY WITH VERTICAL

Pitfalls of mapping a large Turkish consanguineous family with vertical monilethrix inheritance: Monilethrix, a rare autosomal dominant disease characterized by hair fragility and follicular hyperkeratosis, is caused by mutations in three type It hair cortex keratins. The human keratin family comprises 54 members, 28 type I and 26 type II. The phenotype shows variable penetrance and results ill hair fragility and patchy dystrophic alopecia. In our study, Monilethrix was diagnosed oil the basis of clinical characteristics and microscopic examination in a family with 11 affected members. Haplotype analysis was performed by three Simple Tandem Repeat markers (STR) and KRT86 gene was sequenced for the identification of the disease causing mutation. In the results of this, autosomal dominant mutation (E402K) in exon 7 of KRT86 gene was identified as a cause of Moniltherix in the large family from Turkey