Holocytochrome C Synthase (HCCS)

Based on its chromosomal location and its role in the mitochondrial respiratory chain, HCCS was considered a candidate gene for Rett syndrome (RTT). The genomic structure of the gene, which occupies an 11-kb region and consists of 7 exons, was determined. No mutational abnormality of the gene was found in 20 RTT patients (Van den Veyver et al., 1998).

The human gene, symbolized HCCS, and the corresponding murine gene characterized by Schaefer et al. (1996) share 83% nucleotide sequence identity and 85% amino acid identity. The authors stated that, because of the lack of a neuromuscular phenotype in MLS, it is uncertain how the deletion of a mitochondrial holocytochrome synthetase would contribute to the phenotype seen in MLS.