Mental retardation is a major symptom of MSS which suggests a role of SIL1 in the development of the central nervous system, but how SIL1 functions remains unclear.
Mental retardation in our patient and absence of the b-wave in his electroretinogram indicate that central nervous functions of dystrophin isoforms also depend on the presence of cysteine 3340.
FMR1 is an RNA-binding protein that is either absent or mutated in patients affected by the fragile X syndrome, the most common inherited cause of mental retardation in humans.
BBS2 is a clinically and genetically heterogeneous group of disorders resulting in rod-cone dystrophy, obesity, postaxial polydactyly, renal dysfunction, and mental retardation, which were very recently associated with a novel gene designated BBS2.
FKRP mutations account for a broad spectrum of patients with muscular dystrophy, from a severe congenital form with or without mental retardation (MDC1C) to a much milder limb-girdle muscular dystrophy (LGMD2I).
Drebrin has been reported to be engaged in dendritic-cytoskeleton modulation at synapses, and such a novel NXF signaling system on neural gene promoter may be a molecular target of the adverse effects of Sim2 in the mental retardation of Down's syndrome.
FMR1 premutation alleles uniquely produce FMR1 transcripts with an elongated CGG repeat, leading to the hypothesis that premutant transcripts cause the neurodegenerative disease in carriers.Recently Jin et al. demonstrated, in Drosophila, that FMR1 premutation RNA causes neurodegeneration.
MECP2 gene mutations responsible for Rett syndrome have also been found in male patients with mental retardation, sometimes associated with different neurologic abnormalities.
VCX-A deficiency has been shown previously to be associated with mental retardation and NLGN4 mutations lead to mental retardation in conjunction with autism.