The role of CNVs in the etiology of rare autosomal recessive disorders: the example of TRAPPC9-associated intellectual disability.

Introduction: A large number of genes involved in autosomal recessive forms of intellectual disability (ID) were identified over the past few years through whole-exome sequencing (WES) or whole-genome sequencing in consanguineous families. Disease-associated variants in TRAPPC9 were reported in eight multiplex consanguineous sibships from different ethnic backgrounds, and led to the delineation of the phenotype. Affected patients have microcephaly, obesity, normal motor development, severe ID, and language impairment and brain anomalies.

Breakpoint mapping by next generation sequencing reveals causative gene disruption in patients carrying apparently balanced chromosome rearrangements with intellectual deficiency and/or congenital malformations.

Background: Apparently balanced chromosomal rearrangements (ABCR) are associated with an abnormal phenotype in 6% of cases. This may be due to cryptic genomic imbalances or to the disruption of genes at the breakpoint. However, breakpoint cloning using conventional methods (ie, fluorescent in situ hybridisation (FISH), Southern blot) is often laborious and time consuming.