FG syndrome: The FGS2 locus revisited

Molecular and clinical analyses with neuropsychological assessment of a case of del(10)(q26.2qter) without intellectual disability: Genomic and transcriptomic combined approach and review of the literature

Terminal deletion of the long arm of the chromosome 10 is a rare but well known abnormality, with a large phenotypic variability. Very few data are available about subtelomeric deletion 10q26 patients without intellectual disability. Herein, we report the case of a young adult with a classical 10q26.2qter deletion. She exhibited mainly short stature at birth and in childhood/adulthood without intellectual disability or behavioral problems. After clinical and neuropsychological assessments, we performed genomic array and transcriptomic analysis and compared our results to the data available in the literature. The patient presents a 6.525 Mb heterozygous 10q26.2qter deletion, encompassed 48 genes. Among those genes, DOCK1, C10orf90, and CALY previously described as potential candidate genes for intellectual disability, were partially or completed deleted. Interestingly, they were not deregulated as demonstrated by transcriptomic analysis. This allowed us to suggest that the mechanism involved in the deletion 10qter phenotype is much more complex that only the haploinsufficiency of DOCK1 or other genes encompassed in the deletion. Genomic and transcriptomic combined approach has to be considered to understand this pathogenesis. © 2016 Wiley Periodicals, Inc.

Combined deletion of two Condensin II system genes (NCAPG2 and MCPH1) in a case of severe microcephaly and mental deficiency

7qter deletion syndrome includes prenatal and/or postnatal growth retardation, microcephaly, psychomotor delay or mental retardation and a characteristic dysmorphism. If clinical features are well described, the molecular mechanisms underlying the 7qter deletion syndrome remain unknown. Those deletions usually arise de novo. Here, we describe a young boy with an abnormal phenotype consistent with a 7qter deletion syndrome. High resolution genomic analysis (Affymetrix Human Genome Wide SNP 6.0) revealed a 7q36.3 deletion encompassing NCAPG2, ESYT2, WDR60 and VIPR2, inherited from his asymptomatic father and paternal grandfather. In addition, the patient also harbored a MCPH1 deletion inherited from his healthy mother. Combined NCAPG2 and MCPH1 deletions were correlated with low mRNA levels and protein expression in the patient. MCPH1 and NCAPG2 proteins interaction is known to control chromosome structure and we thus propose that double heterozygosity for null mutations of those two genes of the Condensin II system contribute to mental deficiency with severe microcephaly phenotype.

Dysregulation of FOXG1 pathway in a 14q12 microdeletion case

"FOXG1 syndrome" includes postnatal microcephaly, severe intellectual disability with absence of language and agenesis of the corpus callosum. When the syndrome is associated with large 14q12q13 deletions, the patients present characteristic facial dysmorphism. Although all reports were based on genomic analysis, recently a FOXG1 regulatory elements deletion, associated with down regulated mRNA, suggested an implication of FOXG1 pathway. Herein, we report on a young boy with a phenotype consistent with a FOXG1 syndrome. He had a de novo translocation t(6;14)(q22.1;q12) associated with a heterozygous 14q12.2q13 deletion encompassing FOXG1. Subsequently, we investigated his transcriptomic profile on lymphoblastoïd cell lines and/or fibroblasts and showed that FOXG1 was commonly down-regulated. Moreover, several other FOXG1 pathway genes were also disturbed. Our data and review of previous reports highlight dysregulation of FOXG1 pathway as the cause of the "FOXG1 syndrome" developmental disorder.