Small EDRK Rich Factor 1A (SERF1A)

The full-length human cDNA was named H4F5, and its mouse counterpart M4f5, until an appropriate function can be assigned to the 2 genes. The proteins displayed 97% amino acid similarity to one another and both genes were ubiquitously expressed with highest RNA levels in testis. In addition, H4F5 has a larger 1.8-kb isoform, H4F5L, with a predicted 110-amino acid open reading frame that results from alternative splicing of exon 3. In contrast to the 0.6-kb mouse and 0.7-kb human 4F5S isoforms, the 1.8-kb H4F5L transcript is predominantly expressed in heart, brain, and skeletal muscle. Both isoforms are also expressed throughout the central nervous system, including spinal cord, which is the tissue primarily affected in SMA. H4F5 was found to lie closer to SMN1 than any previously identified gene in the region.