Biallelic HERC1 mutations in a syndromic form of overgrowth and intellectual disability.

We report two Colombian siblings affected by overgrowth, intellectual disability and facial dysmorphism. Exome (via NGS) and Sanger sequencing revealed that biallelic sequence variants in a novel gene (HERC1) might be related to the disease pathogenesis. These results provide useful data for future genotype-phenotype correlations and for a molecular diagnosis of overgrowth.

A novel TGM1 mutation, leading to multiple splicing rearrangements, is associated with autosomal recessive congenital ichthyosis.

Autosomal recessive congenital ichthyosis (ARCI) is a group of rare, clinically heterogeneous skin disorders that affect cornification. ARCI includes lamellar ichthyosis, congenital ichthyosiform erythroderma and harlequin ichthyosis. TGM1 mutations cause > 50% of ARCI cases in the USA. We report two siblings with ARCI. They were found to carry a novel aetiological TGM1 mutation, which leads to the synthesis of multiple abnormal transcripts. These molecules resulted from three independent mechanisms: intron retention, exon skipping and activation of expand cryptic splice sites. Taken together, our findings expand the known TGM1 mutation repertoire, and provide an insight into the molecular mechanisms leading to ARCI phenotypes. These results could be useful for genetic counselling and future potential genotype-phenotype correlations.

CFTR mutations in three Latin American countries.

We analyzed 192 cystic fibrosis (CF) alleles in three Latin American countries: Mexico, Colombia, and Venezuela. Mutation screening was performed by polymerase chain reaction (PCR) and a reverse dot blot detection kit that enables determination of 16 of the most common CF mutations worldwide. Mutations were detected in 47.9% of the screened CF alleles. The most prevalent CF allele was DeltaF508 (39. 6%). The remaining 16 non-DeltaF508 detectable mutations represented 8.3% of the CF alleles. Among them, the G542X, N1303K, and 3849+10kb C>T were the most common. Although the frequency of DeltaF508 described here is lower than that reported for Caucasian populations, including in Spain, it is remarkable that mutation prevalences found in this study resemble those observed in Spain. Two of these mutations, G542X and 3849+10kb C>T, that were relevant in this analysis, have a particularly high incidence in Spanish communities. The low frequency of DeltaF508 described here may be explained by the Amerindian, Caucasian, and Black admixture that occurred in Latin America after the discovery of the New World, and also by the probable occurrence of mutations contributed by the original natives, which were undetectable in this analysis.

Tandem duplication of proximal 5q.

A 3.5-year-old boy with a de novo tandem duplication 5q11.1----5q15 is reported. Since the physical stigmata of seven liveborn cases with 5q proximal duplications are variable and inconspicuous, a recognizable syndrome could not be delineated. On the contrary, the associated developmental delay seems to be severe in duplications extending into 5q22 and mild in duplications 5q11----q13.