Homozygous deletion of an 80 kb region comprising part of DNAJC6 and LEPR genes on chromosome 1P31.3 is associated with early onset obesity, mental retardation and epilepsy.

CONTEXT

The genomic organization of the LEPR gene is complex and generates three independent transcripts whose respective functions are still poorly understood.

METHODS/RESULTS: We describe here a 7-year old patient with a homozygous 80 kb deletion in the chromosomal 1p31.3 region with early onset obesity, mental retardation and epilepsy. The deleted region comprises the proximal promoter and exons 1 and 2 of the LEPR gene and exons 5 to 19 of the DNAJC6 gene. The deletion leads to the deficiency of all canonical OB-R isoforms but maintains the B219 OB-R short isoforms controlled by the preserved second LEPR promoter. The DNAJC6 gene encodes auxilin-1, a protein required for clathrin-dependent recycling of synaptic vesicles in neurons that is possibly at the origin of the mental retardation and epilepsy phenotype. The obese phenotype and the absence of signaling-competent OB-R are consistent with previously reported individuals with OB-R deficiency. The deletion eliminates an additional transcript of the LEPR gene that encodes endospanin-1, a protein that has been genetically and biochemically linked to OB-R function.

CONCLUSIONS

Our study confirms the phenotype of individuals with OB-R deficiency and postulates the effects of auxilin-1 deficiency (mental retardation/epilepsy) and endospanin-1 deficiency (OB-R specific functions) in humans.