Alternative titles; symbols
HGNC Approved Gene Symbol: SMCP
Cytogenetic location: 1q21.3 Genomic coordinates (GRCh38): 1:152,878,322-152,885,047 (from NCBI)
By sequence analysis of the human and mouse MCSP cDNAs Aho et al. (1996) revealed that the 5-prime and 3-prime untranslated sequences are more conserved (71%) than the coding sequences (59%). The open reading frame encodes a 116-amino acid protein and lacks the UGA codons that have been reported to encode the selenocysteines in the N-terminal of the deduced mouse protein. The deduced human protein showed a low degree of amino acid sequence identity to the mouse protein (39%). The striking homology lies in the dicysteine motifs. Northern and Southern zooblot analyses revealed that the MCSP gene in human, baboon, and bovine is more conserved than its counterparts in mouse and rat. Northern blot and in situ hybridization experiments demonstrated that expression of the human MCSP gene is restricted to haploid spermatids.
Hawthorne et al. (2006) determined that the SMCP protein has a conserved tripartite structure consisting of a short N-terminal segment, a central segment containing short tandem repeats rich in cysteine, proline, glutamine, and lysine, and a C-terminal segment containing no repeats, few cysteines, and a C-terminal lysine. The SMCP 5-prime UTR in several mammalian species, including human, has 2 upstream open reading frames that are expected to reduce translation of the major SMCP reading frame. The 5-prime UTR of mouse, rat, and human SMCP also has a predicted stem loop that is involved in regulation of SMCP expression. Hawthorne et al. (2006) found that Smcp mRNA was much more abundant in mouse and dog testis than in human testis.
The mitochondrial capsule selenoprotein is 1 of 3 proteins that are important for the maintenance and stabilization of the crescent structure of the sperm mitochondria. Aho et al. (1996) noted that mitochondria in the sperm differ from those in somatic cells in their morphology and arrangement. They are flattened, elongated, and arranged circumferentially into a tight helical coil around the tail-dense fibers of the mature sperm. Rats on a selenium-deficient diet show reduced sperm motility and disorganization of the sperm mitochondria.
Aho et al. (1996) determined that the single intron in the human MCSP gene is about 6 kb and interrupts the 5-prime untranslated region at a position equivalent to that in the mouse and rat genes.
By isotopic in situ hybridization, Aho et al. (1996) mapped the MCSP gene to chromosome 1q21.
By genomic sequence analysis, Hawthorne et al. (2006) mapped the SMCP gene to the middle of the epidermal differentiation complex (EDC), a large gene cluster that functions in forming epithelial barriers, on chromosome 1q21. They mapped the mouse Smcp gene to the EDC on chromosome 3F1, which shares homology of synteny with human chromosome 1q21. Hawthorne et al. (2006) hypothesized that Smcp originated from an EDC gene that acquired spermatogenic cell-specific properties.
Nayernia et al. (2002) found that some Smcp-null male mice were infertile, depending upon their genetic background. Spermatogenesis and mating in all Smcp-null males were normal, and electron microscopic examination demonstrated normal structures of sperm head, mitochondria, and tail in all mutant male mice. Infertility in the sensitive males was due to reduced motility of the spermatozoa and decreased capability of the spermatozoa to penetrate oocytes. All Smcp-null female mice were fertile.
Aho, H., Schwemmer, M., Tessmann, D., Murphy, D., Mattei, G., Engel, W., Adham, I. M. Isolation, expression, and chromosomal localization of the human mitochondrial capsule selenoprotein gene (MCSP). Genomics 32: 184-190, 1996. [PubMed: 8833144] [Full Text: https://doi.org/10.1006/geno.1996.0104]
Hawthorne, S. K., Goodarzi, G., Bagarova, J., Gallant, K. E., Busanelli, R. R., Olend, W. J., Kleene, K. C. Comparative genomics of the sperm mitochondria-associated cysteine-rich protein gene. Genomics 87: 382-391, 2006. [PubMed: 16325371] [Full Text: https://doi.org/10.1016/j.ygeno.2005.09.010]
Nayernia, K., Adham, I. M., Burkhardt-Gottges, E., Neesen, J., Rieche, M., Wolf, S., Sancken, U., Kleene, K., Engel, W. Asthenozoospermia in mice with targeted deletion of the sperm mitochondrion-associated cysteine-rich protein (Smcp) gene. Molec. Cell. Biol. 22: 3046-3052, 2002. [PubMed: 11940662] [Full Text: https://doi.org/10.1128/MCB.22.9.3046-3052.2002]