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Sperm-binding fibronectin type II-module proteins are genetically linked and functionally related
Mahnaz Ekhlasi-Hundrieser1, Bettina Schäfer, Ute Philipp
1Department of Reproductive Biology, University of Veterinary Medicine Hannover, Bünteweg 2, 30559 Hannover, Germany. mahnaz.ekhlasi@tiho-hannover.de
Abstract:
Fibronectin type II (Fn2) module-containing proteins in the male genital tract are characterized by different numbers of Fn2 modules. Predominantly two classes exist which are distinct by having either two or four Fn2 modules. Minor variants with three Fn2 modules were also found in the human and the porcine epididymis. To reveal their relationship, mRNAs and proteins of representatives of these classes were studied in human, in Sus scrofa, and in rodents. Adult boars expressed members of both classes, i.e. ELSPBP1 and pB1, in subsequent regions of the epididymis, and both were under androgenic control. Human and rodent epididymides, on the other hand, alternatively contained only representatives of one of these two classes, i.e. ELSPBP1 in the human and two different pB1-related counterparts in rodents. ELSPBP1 and pB1-related genomic sequences were closely linked in chromosomal regions HSA 19q and SSC 6 q11-q21; conserved synteny between these regions is well established. On the other hand, in a syntenic region on mouse chromosome 7, ELSPBP1-related sequences were lacking. Tight binding to the sperm membrane via a choline-mediated mechanism was a common feature of the two classes of Fn2-module proteins, suggesting related function(s). However, differences in their regionalized expression patterns along the male genital tract as well as in association sites on the sperm surface suggested a species-specific sequential order in sperm binding.
Insights
Male reproductive tract proteins with fibronectin type II (Fn2) modules, such as ELSPBP1 and pB1, exhibit species-specific expression and binding to sperm. Their functions are conserved but ordered sequentially, depending on the species.
Area of Science:
- Reproductive biology
- Molecular and cellular biology
- Protein biochemistry
Background:
- Fibronectin type II (Fn2) module-containing proteins are present in the male genital tract.
- These proteins exist in distinct classes, primarily with two or four Fn2 modules, and variants with three modules are found in humans and pigs.
Purpose of the Study:
- To investigate the relationship and functional similarities/differences of Fn2 module-containing proteins.
- To understand their expression patterns and sperm-binding mechanisms across species.
Main Methods:
- Analysis of mRNA and protein expression in human, porcine (Sus scrofa), and rodent reproductive tracts.
- Genomic sequence analysis to identify gene linkage and synteny.
- Investigation of sperm membrane binding mechanisms.
Main Results:
- Adult boars express both ELSPBP1 and pB1 proteins in different epididymal regions under androgenic control.
- Human and rodent epididymides show alternative expression of either ELSPBP1 or pB1-related proteins.
- Genomic sequences for ELSPBP1 and pB1 are closely linked, with conserved synteny in humans and pigs, but ELSPBP1 sequences are absent in a syntenic mouse region.
- Both protein classes bind tightly to sperm membranes via a choline-mediated mechanism.
Conclusions:
- Fn2 module-containing proteins (ELSPBP1 and pB1) share conserved sperm-binding functions but exhibit species-specific expression patterns in the male genital tract.
- This suggests a species-specific sequential order in sperm binding, contributing to reproductive processes.
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