Neural progenitor proliferation and migration influence brain size during neurogenesis. We report an autosomal recessive microcephaly syndrome cosegregating with a homozygous balanced translocation between chromosomes 3p and 10q, and we show that a position effect at the breakpoint on chromosome 3 silences the eomesodermin transcript (EOMES), also known as T-box-brain2 (TBR2). Together with the expression pattern of EOMES in the developing human brain, our data suggest that EOMES is involved in neuronal division and/or migration. Thus, mutations in genes encoding not only mitotic and apoptotic proteins but also transcription factors may be responsible for malformative microcephaly syndromes.

BackgroundThe clinical significance of 16p13.11 duplications remains controversial while frequently detected in patients with developmental delay (DD), intellectual deficiency (ID) or autism spectrum disorder (ASD). Previously reported patients were not or poorly characterised. The absence of consensual recommendations leads to interpretation discrepancy and makes genetic counselling challenging. This study aims to decipher the genotype–phenotype correlations to improve genetic counselling and patients’ medical care.MethodsWe retrospectively analysed data from 16 013 patients referred to 12 genetic centers for DD, ID or ASD, and who had a chromosomal microarray analysis. The referring geneticists of patients for whom a 16p13.11 duplication was detected were asked to complete a questionnaire for detailed clinical and genetic data for the patients and their parents.ResultsClinical features are mainly speech delay and learning disabilities followed by ASD. A significant risk of cardiovascular disease was noted. About 90% of the patients inherited the duplication from a parent. At least one out of four parents carrying the duplication displayed a similar phenotype to the propositus. Genotype–phenotype correlations show no impact of the size of the duplicated segment on the severity of the phenotype. However, NDE1 and miR-484 seem to have an essential role in the neurocognitive phenotype.ConclusionOur study shows that 16p13.11 microduplications are likely pathogenic when detected in the context of DD/ID/ASD and supports an essential role of NDE1 and miR-484 in the neurocognitive phenotype. Moreover, it suggests the need for cardiac evaluation and follow-up and a large study to evaluate the aortic disease risk.

This study compares the results of cytogenetic analysis of chromosomal abnormalities in the Moroccan population with other countries and research centers. This comparison will help Moroccan clinicians to determine the priority for requesting a cytogenetic analysis in individual cases.

BackgroundWe report clinical and molecular cytogenetic characterization of a 2 year-old girl with 19p13.2p13.12 microdeletion and compare her clinical features with those of three other patients reported before.ResultArray comparative genomic hybridization (aCGH) revealed in the present patient a de novo microdeletion of 1.45 Mb within 19p13.2p13.12. The deletion includes seven OMIM genes: MAN2B1, RNASEH2A, KLF1, GCDH, NFIX, CACNA1A and CC2D1A.DiscussionThe present case and three other patients with partially overlapping 19p13 microdeletion share the following features: psychomotor and language delay, intellectual disability, seizures, hypotonia, skeletal anomalies and facial dysmorphism. The smallest region of overlapping between all four reported patients is around 300 kb and spans only two genes: NFIX and CACNA1A. Their haploinsufficincy could be the base for the phenotype -genotype correlation.