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Published on: July 30, 2011
Rapidly evolving marmoset MSMB genes are differently expressed in the male genital tract
Ake Lundwall1, Olivia Larne, Penelope L Nayudu
1Lund University, Department of Laboratory Medicine, Division of Clinical Chemistry, University Hospital MAS, Malmö, Sweden. ake.lundwall@med.lu.se
Background:
Beta-microseminoprotein, an abundant component in prostatic fluid, is encoded by the potential tumor suppressor gene MSMB. Some New World monkeys carry several copies of this gene, in contrast to most mammals, including humans, which have one only. Here we have investigated the background for the species difference by analyzing the chromosomal organization and expression of MSMB in the common marmoset (Callithrix jacchus).
Methods:
Genes were identified in the Callithrix jacchus genome database using bioinformatics and transcripts were analyzed by RT-PCR and quantified by real time PCR in the presence of SYBR green.
Results:
The common marmoset has five MSMB: one processed pseudogene and four functional genes. The latter encompass homologous genomic regions of 32-35 kb, containing the genes of 12-14 kb and conserved upstream and downstream regions of 14-19 kb and 3-4 kb. One gene, MSMB1, occupies the same position on the chromosome as the single human gene. On the same chromosome, but several Mb away, is another MSMB locus situated with MSMB2, MSMB3 and MSMB4 arranged in tandem. Measurements of transcripts demonstrated that all functional genes are expressed in the male genital tract, generating very high transcript levels in the prostate. The transcript levels in seminal vesicles and testis are two and four orders of magnitude lower. A single gene, MSMB3, accounts for more than 90% of MSMB transcripts in both the prostate and the seminal vesicles, whereas in the testis around half of the transcripts originate from MSMB2. These genes display rapid evolution with a skewed distribution of mutated nucleotides; in MSMB2 they affect nucleotides encoding the N-terminal Greek key domain, whereas in MSMB3 it is the C-terminal MSMB-unique domain that is affected.
Conclusion:
Callitrichide monkeys have four functional MSMB that are all expressed in the male genital tract, but the product from one gene, MSMB3, will predominate in seminal plasma. This gene and MSMB2, the predominating testicular gene, have accumulated mutations that affect different parts of the translation products, suggesting an ongoing molecular specialization that presumably yields functional differences in accessory sex glands and testis.
Insights
New World monkeys, like the marmoset, possess multiple functional beta-microseminoprotein (MSMB) genes, unlike humans. These genes are expressed in the male reproductive tract, with distinct genes dominating different tissues and showing signs of rapid evolution.
Area of Science:
- Genomics
- Evolutionary Biology
- Molecular Biology
Background:
- Beta-microseminoprotein (MSMB) is a key prostatic fluid component encoded by a gene with potential tumor suppressor functions.
- While most mammals have one MSMB gene, certain New World monkeys exhibit multiple copies, suggesting evolutionary divergence.
Purpose of the Study:
- To investigate the genomic organization and expression of the MSMB gene in the common marmoset (Callithrix jacchus).
- To understand the evolutionary basis for the difference in MSMB gene copy number between species.
Main Methods:
- Utilized bioinformatics to identify MSMB genes in the marmoset genome database.
- Analyzed gene transcripts using RT-PCR and quantified expression levels via real-time PCR with SYBR green.
Main Results:
- The common marmoset possesses four functional MSMB genes and one pseudogene, arranged in distinct chromosomal locations.
- All functional MSMB genes are expressed in the male genital tract, with high levels in the prostate.
- MSMB3 is the predominant transcript in the prostate and seminal vesicles, while MSMB2 dominates in the testis, with evidence of rapid evolution affecting different protein domains.
Conclusions:
- Callitrichid monkeys have four expressed MSMB genes in the male reproductive system, with MSMB3 dominating seminal plasma and MSMB2 the testis.
- Evidence suggests ongoing molecular specialization and functional divergence of MSMB genes in these primates.
