Expression analysis and protein localization of the human HPC-1/syntaxin 1A, a gene deleted in Williams syndrome.

The HPC-1/syntaxin 1A (STX1A) gene maps to the Williams syndrome (WS) commonly deleted region on chromosome 7q11.23 and encodes a protein implicated in the docking of synaptic vesicles with the presynaptic plasma membrane. To assess the potential role of STX1A in the WS phenotype, we carried out expression studies at the RNA and protein levels, in fetal and adult human tissues. RNA in situ hybridization on human embryo sections showed strong STX1A expression in spinal cord and ganglia. However, in adulthood, this gene was preferentially expressed in brain, as shown by Northern blot and RT-PCR experiments. Marked expression levels were observed in cerebellum and cerebral cortex. The STX1A protein was prevalently distributed in the molecular layer of the cerebellar cortex. A qualitative and quantitative analysis using a specific anti-STX1A antibody did not disclose any significant difference among frontal, temporal, and occipital poles of the human adult cortex in the two hemispheres. This is the first study focused on STX1A expression in humans. Our results indicate that this gene is strongly expressed in cerebral areas involved in cognitive process, supporting a likely role in the neurological symptoms of WS.