Expanding the clinical spectrum of the 'HDAC8-phenotype' - implications for molecular diagnostics, counseling and risk prediction.

Cornelia de Lange syndrome (CdLS) is a clinically heterogeneous disorder characterized by typical facial dysmorphism, cognitive impairment and multiple congenital anomalies. Approximately 75% of patients carry a variant in one of the five cohesin-related genes NIPBL, SMC1A, SMC3, RAD21 and HDAC8. Herein we report on the clinical and molecular characterization of 11 patients carrying 10 distinct variants in HDAC8. Given the high number of variants identified so far, we advise sequencing of HDAC8 as an indispensable part of the routine molecular diagnostic for patients with CdLS or CdLS-overlapping features. The phenotype of our patients is very broad, whereas males tend to be more severely affected than females, who instead often present with less canonical CdLS features. The extensive clinical variability observed in the heterozygous females might be at least partially associated with a completely skewed X-inactivation, observed in seven out of eight female patients. Our cohort also includes two affected siblings whose unaffected mother was found to be mosaic for the causative mutation inherited to both affected children. This further supports the urgent need for an integration of highly sensitive sequencing technology to allow an appropriate molecular diagnostic, genetic counseling and risk prediction.

Broadening of cohesinopathies: exome sequencing identifies mutations in ANKRD11 in two patients with Cornelia de Lange-overlapping phenotype.

Cornelia de Lange syndrome (CdLS) and KBG syndrome are two distinct developmental pathologies sharing common features such as intellectual disability, psychomotor delay, and some craniofacial and limb abnormalities. Mutations in one of the five genes NIPBL, SMC1A, SMC3, HDAC8 or RAD21, were identified in at least 70% of the patients with CdLS. Consequently, additional causative genes, either unknown or responsible of partially merging entities, possibly account for the remaining 30% of the patients. In contrast, KBG has only been associated with mutations in ANKRD11. By exome sequencing we could identify heterozygous loss-of-function mutations in ANKRD11 in two patients with the clinical diagnosis of CdLS. Both patients show features reminiscent of CdLS such as characteristic facies as well as a small head circumference which is not described for KBG syndrome. Patient A, who carries the mutation in a mosaic state, is a 4-year-old girl with features reminiscent of CdLS. Patient B, a 15-year-old boy, shows a complex phenotype which resembled CdLS during infancy, but has developed to a more KBG overlapping phenotype during childhood. These findings point out the importance of screening ANKRD11 in young CdLS patients who were found to be negative for mutations in the five known CdLS genes.

Identification of a single SNP that affects the promoter activity in the Moroccan prolific D'man breed.

Common Moroccan breeds D'man, Sardi, and Timahdite have been found to differ regarding litter size. D'man is known for its high prolificacy (2-7 lambs), whereas Timahdite and Sardi are normally prolific (1-2 lambs). Here, we aimed to identify genetic variants in the ß promoter and to study the promoter activity amongst these breeds using sequencing for the former and the in vitro luciferase assay for the latter. Sequence analysis revealed 16 genetic variants among these common breeds. Luciferase assay analysis demonstrated a higher promoter activity in D'man compared to the Sardi/Timahdite breeds. A small region of 541 bp was further characterized as possessing a high promoter activity. This region contains 2 palindromic sequences and 7 variants. Based on in silico analysis, only 2 variants at position -559 and -568 were found to be informative. These 2 variants were localized within a region rich in transcription factor binding sites including GATA-1/GATA-2, E4/th1, CP2, and c-Ets. Using site-directed mutagenesis, only the variant at position -559 A/G was found to substantially influence the promoter activity. Taken together, differences in the level of ß transcription among highly and minimally prolific Moroccan breeds were demonstrated and a novel single variant was identified that could explain this difference.