SOBP is mutated in syndromic and nonsyndromic intellectual disability and is highly expressed in the brain limbic system.

Intellectual disability (ID) affects 1%-3% of the general population. We recently reported on a family with autosomal-recessive mental retardation with anterior maxillary protrusion and strabismus (MRAMS) syndrome. One of the reported patients with ID did not have dysmorphic features but did have temporal lobe epilepsy and psychosis. We report on the identification of a truncating mutation in the SOBP that is responsible for causing both syndromic and nonsyndromic ID in the same family. The protein encoded by the SOBP, sine oculis binding protein ortholog, is a nuclear zinc finger protein. In mice, Sobp (also known as Jxc1) is critical for patterning of the organ of Corti; one of our patients has a subclinical cochlear hearing loss but no gross cochlear abnormalities. In situ RNA expression studies in postnatal mouse brain showed strong expression in the limbic system at the time interval of active synaptogenesis. The limbic system regulates learning, memory, and affective behavior, but limbic circuitry expression of other genes mutated in ID is unusual. By comparing the protein content of the +/jc to jc/jc mice brains with the use of proteomics, we detected 24 proteins with greater than 1.5-fold differences in expression, including two interacting proteins, dynamin and pacsin1. This study shows mutated SOBP involvement in syndromic and nonsyndromic ID with psychosis in humans.

X-linked mental retardation with alacrima and achalasia-Triple A syndrome or a new syndrome?

We describe a consanguineous Israeli Arab kindred with five males in two interrelated families with intellectual disabilities, alacrima, achalasia, and mild autonomic dysfunction. Adrenal function is normal. Their phenotype is similar to the phenotype observed in autosomal recessive Triple A syndrome except for the presence of mental retardation in all affected individuals. The pedigree is compatible with either X-linked or autosomal recessive inheritance. Sequencing of the AAAS gene causing autosomal recessive Triple A syndrome did not reveal mutations. Genotyping of affected family members identified a 16.4 Mb continuous segment of identical alleles shared by the patients between markers rs2748314 and rs5906782 on Xp11.23-p21, establishing linkage to chromosome X. This study further confirms genetic heterogeneity in Triple A syndrome and points to a clinically different subtype including significant cognitive impairment.