HGNC Approved Gene Symbol: SEMG2
Cytogenetic location: 20q13.12 Genomic coordinates (GRCh38) : 20:45,221,373-45,224,458 (from NCBI)
Ulvsback et al. (1992) characterized the genes for semenogelin I (182140) and II, the major protein constituents of the human seminal fluid, by 3 overlapping clones in bacteriophage lambda, encompassing 31.5 kb of genomic DNA. They found that the 2 genes are located 11.5 kb apart in the region 20q12-q13.1. Both genes are relatively compact, spanning only 2.7 and 3.1 kb, respectively. The transcription units are composed of 3 exons, of which the first encodes the signal peptide, the second encodes secreted protein, and the third contains solely 3-prime, noncoding nucleotides. The nucleotide sequences exhibited a similarity of close to 90% in the exons and greater than 80% in the introns and flanking nucleotides.
Postcopulatory sperm competition is a key aspect of sexual selection and is believed to drive the rapid evolution of both reproductive physiology and reproduction-related genes. It is well established that mating behavior determines the intensity of sperm competition, with polyandry (i.e., female promiscuity) leading to fiercer sperm competition than monandry. Studies in mammals, particularly primates, showed that, owing to greater sperm competition, polyandrous taxa generally have physiologic traits that make them better adapted for fertilization than monandrous species, including bigger testes, larger seminal vesicles, higher sperm counts, richer mitochondrial loading in sperm, and more prominent semen coagulation. Dorus et al. (2004) showed that the degree of polyandry can also impact the dynamics of molecular evolution. Specifically, they showed that the evolution of the gene encoding semenogelin II, a main structural component of semen coagulum, is accelerated in polyandrous primates relative to monandrous primates.
Dorus, S., Evans, P. D., Wyckoff, G. J., Choi, S. S., Lahn, B. T. Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity. Nature Genet. 36: 1326-1329, 2004. [PubMed: 15531881] [Full Text: https://doi.org/10.1038/ng1471]
Ulvsback, M., Lazure, C., Lilja, H., Spurr, N. K., Rao, V. V., Loffler, C., Hansmann, I., Lundwall, A. Gene structure of semenogelin I and II: the predominant proteins in human semen are encoded by two homologous genes on chromosome 20. J. Biol. Chem. 267: 18080-18084, 1992. [PubMed: 1517240]