Comparison of Siglec-1 protein networks and expression patterns in sperm and male reproductive tracts of mice, rats, and humans

Abstract

Background: Sialic acid-binding immunoglobulin-like lectin 1 (Siglec-1) is a transmembrane glycoprotein involved in the sialic acid (Sia)-dependent regulation of the immune system. Siglec-1 expression has recently been identified in the male reproductive tract (MRT) of several species, including humans, cattle, horses, and sheep, and may play a role in modulating fertility in a Sia-dependent manner.

Materials and methods: In this study, protein-protein interaction (PPI) analysis of Siglec-1 was conducted to identify associated network protein conservation, and the expression of Siglec-1 in the MRT of mice and rats, including their accessory sex glands and spermatozoa was determined by immunostaining.

Results: Network analysis of proteins with Siglec-1 in mice and rats demonstrated significant similarity to human Siglec-1 networks, suggesting a similar conservation of network proteins between these species and, hence, a potential conservation role in immune modulation and function. Specific immunostaining patterns of mouse and rat testes, epididymis, ductus deferens, accessory sex gland tissues, and sperm were detected using human Siglec-1. These results confirmed that the human Siglec-1 antibody could cross-react with mouse and rat Siglec-1, suggesting that the specific expression patterns of Siglec-1 in the MRT and sperm of both mice and rats are similar to those observed in other species.

Conclusions: The conservation of Siglec-1 expression patterns in sperm and within the MRT and the similarity of protein networks for Siglec-1 across species suggest that Siglec-1 may function in a similar manner across species. These results also suggest that rodents may serve as a valuable model system for exploring the function of Siglecs in the reproductive system across species and their potential role in modulating fertility in a Sia-dependent manner.

Keywords: female reproductive tract; male reproductive tract; protein–protein interaction; sialic acid; sialic acid-binding immunoglobulin-like lectin-1.

Figure-1

Immunostaining of Siglec-1 in the male reproductive tract and accessory glands of mice using anti-human Siglec-1 antibody. Hematoxylin and eosin staining was used to identify the main structures of MRT and accessory glands of mice. Representative images stained with the primary antibody along with control (stained with secondary antibody) are shown. Siglec-1=Sialic acid-binding immunoglobulin-like lectin 1, MRT=Male reproductive tract.

Figure-2

(a) Immunostaining of Siglec-1 in the accessory glands and spleen of mice using human Siglec-1 antibody. Hematoxylin and eosin staining was used to identify the main structures of MRT and accessory glands of mice. Representative images stained with the primary antibody along with control (stained with secondary antibody) are shown. (b) Histogram represents expression levels of mice Siglec-1 in the male reproductive tract, accessory glands, spleen, and blood of mice using human Siglec-1 antibody. Siglec-1=Sialic acid-binding immunoglobulin-like lectin 1, MRT=Male reproductive tract.

Figure-3

Immunostaining of Siglec-1 in the male reproductive tract and accessory glands of rats using anti-human Siglec-1 antibody. Hematoxylin and eosin staining was used to identify the main structures of MRT of rats and accessory glands. Representative images stained with the primary antibody along with control (stained with secondary antibody) are shown. Siglec-1=Sialic acid-binding immunoglobulin-like lectin 1, MRT=Male reproductive tract.

Figure-4

(a) Immunostaining of Siglec-1 in the accessory glands and spleen of rats using human Siglec-1 antibody. Furthermore, hematoxylin and eosin were used to identify the main structures of MRT and accessory glands of rats. Representative images stained with the primary antibody along with control (stained with secondary antibody) are shown. (b) Histogram represents expression levels of rats Siglec-1 in the male reproductive tract, accessory glands, spleen, and blood of mice detected using human Siglec-1 antibody. Siglec-1=Sialic acid-binding immunoglobulin-like lectin 1, MRT=Male reproductive tract.

Figure-5

Immunofluorescence-based detection of Siglec-1 (yellow arrows) on sperm and blood smear of mice and rats using human Siglec-1 antibody. The corresponding control (secondary antibody) staining is also shown. Siglec-1=Sialic acid-binding immunoglobulin-like lectin 1.

Figure-6

(a) The basic local alignment search tool was used to assess the sequence similarities between the corresponding proteins. (b) The 3D structures of human Siglec-1, mice Siglec-1, and rat Siglec-1 were evaluated for intermolecular interactions using Chimera software by identifying the number of hydrogen bonds formed, and the data are represented as a heatmap. (c) The network proteins of human Siglec-1, mice Siglec-1, and rat Siglec-1 were detected using the STRING database, and the top ten networks were presented. Siglec-1=Sialic acid-binding immunoglobulin-like lectin 1.