No abstract

The strictly regulated expression of most pleiotropic developmental control genes is critically dependent on the activity of long-range cis-regulatory elements. This was revealed by the identification of individuals with a genetic condition lacking coding-region mutations in the gene commonly associated with the disease but having a variety of nearby chromosomal abnormalities, collectively described as cis-ruption disease cases. The congenital eye malformation aniridia is caused by haploinsufficiency of the developmental regulator PAX6. We discovered a de novo point mutation in an ultraconserved cis-element located 150 kb downstream from PAX6 in an affected individual with intact coding region and chromosomal locus. The element SIMO acts as a strong enhancer in developing ocular structures. The mutation disrupts an autoregulatory PAX6 binding site, causing loss of enhancer activity, resulting in defective maintenance of PAX6 expression. These findings reveal a distinct regulatory mechanism for genetic disease by disruption of an autoregulatory feedback loop critical for maintenance of gene expression through development.

Cornelia de Lange syndrome (CdLS) is a rare multisystem disorder characterized by facial dysmorphisms, upper limb abnormalities, growth and cognitive retardation. About half of all patients with CdLS carry mutations in the NIPBL gene. The first Italian CdLS cohort involving 62 patients (including 4 related members) was screened for NIPBL mutations after a clinical evaluation using a quantitative score that integrates auxological, malformation and neurodevelopmental parameters. The patients were classified as having an overall 'severe', 'moderate' or 'mild' phenotype. NIPBL screening showed 26 mutations so classified: truncating (13), splice-site (8), missense (3), in-frame deletion (1) and regulatory (1). The truncating mutations were most frequently found in the patients with a high clinical score, whereas most of the splice-site and all missense mutations clustered in the low-medium score groups. The NIPBL-negative group included patients covering the entire clinical spectrum. The prevalence of a severe phenotype in the mutated group and a mild phenotype in the non-mutated group was statistically significant. In terms of the isolated clinical signs, the statistically significant differences between the mutation-positive and mutation-negative individuals were pre- and post-natal growth deficits, limb reduction, and delayed speech development. The proposed score seems to be a valuable means of prioritizing the patients with CdLS to undergo an NIPBL mutation test.

Background: Mayer-Rokitansky-Kuster-Hauser syndrome (MRKH) consists of congenital aplasia of the uterus and the upper part of vagina due to anomalous development of Müllerian ducts, either isolated or associated with other congenital malformations, including renal, skeletal, hearing and heart defects. This disorder has an incidence of approximately 1 in 4500 newborn girls and the aetiology is poorly understood.