Chorionic Somatomammotropin Hormone 2 (CSH2)

By in situ hybridization, Harper et al. mapped the GH gene cluster to 17q22-q24. Barsh et al. determined that this gene cluster consists of 2 GH genes interspersed with 3 CS genes. All the genes are in the same transcriptional orientation, arranged 5-prime--GH1--CSL--CSA--GHV--CSB--3-prime. Chen et al. reported that the GH gene cluster spans 66,495 bp. Each gene contains 5 exons and encodes a precursor protein of approximately 200 amino acids.

The N-terminal 26 residues of each precursor protein function as a signal sequence. MacLeod et al. stated that the 2 CS genes encode identical secreted 191-amino acid mature proteins. Using Northern blot and RT-PCR analyses, they determined the pattern of CSA and CSB expression during gestation.