Common Marmoset (Callithrix jacchus) Has Two Very Similar Semenogelin Genes as the Result of Gene Conversion

• Published in: Biology of reproduction Vol. 76; no. 4; pp. 604 - 610
• Main Authors: Valtonen-André, Camilla, Olsson, A. Yvonne, Kullberg, Morgan, Nayudu, Penelope L, Lundwall, Åke
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction, Inc 01.04.2007; Society for the Study of Reproduction
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Biologi; Biological and medical sciences; Biological Sciences; Callithrix - genetics; epididymis; Fundamental and applied biological sciences. Psychology; Gene Conversion - physiology; Humans; Male; male reproductive tract; Mammalian male genital system; Molecular Sequence Data; Morphology. Physiology; motility and transport; Natural Sciences; Naturvetenskap; Phylogeny; Seminal Vesicle Secretory Proteins - genetics; seminal vesicles; Sequence Homology; sperm; Vertebrates: reproduction; sperm motility and transport; Motility; Semenogelin; Seminal vesicle; Callithrix jacchus; Semen; Male genital duct; sperm; Gene expression; Male genital system; seminal vesicles; Vertebrata; Epididymis; Mammalia; Gene; Primates; Simioidea; male reproductive tract
• DOI: 10.1095/biolreprod.106.057661
• ISSN: 0006-3363; 1529-7268

The semen coagulum proteins have undergone substantial structural changes during evolution. In primates, these seminal vesicle-secreted proteins are known as semenogelin I (SEMG1) and semenogelin II (SEMG2). Previous studies on the common marmoset (Callithrix jacchus) showed that ejaculated semen from this New World monkey contains semenogelin, but it remained unclear whether it carries both genes or only SEMG1 and no SEMG2, like the closely related cotton-top tamarin (Saguinus oedipus). In this study we show that there are two genes, both expressed in the seminal vesicles. Surprisingly, the genes show an almost perfect sequence identity in a region of 1.25 kb, encompassing nearly half of the genes and containing exon 1, intron 1, and the first 0.9 kb of exon 2. The underlying molecular mechanism is most likely gene conversion, and a phylogenetic analysis suggests that SEMG1 is the most probable donor gene. The marmoset SEMG1 in this report differs from a previously reported cDNA by a lack of nucleotides encoding one repeat of 60 amino acids, suggesting that marmoset SEMG1 displays allelic size variation. This is similar to what was recently demonstrated in humans, but in marmosets the polymorphism was generated by a repeat duplication, whereas in humans it was a deletion. Together, these studies shed new light on the evolution of semenogelins and the mechanisms that have generated the structural diversity of semen coagulum proteins.