# Transcriptomic analysis identifies CXCL12 as a novel candidate gene for litter size in rabbits

## TL;DR

This study identifies CXCL12 as a new gene that may help increase the number of offspring in rabbits by promoting cell growth in the ovaries.

## Contribution

CXCL12 is newly identified as a candidate gene for regulating litter size in rabbits through its effects on granulosa cells.

## Key findings

- CXCL12 promotes granulosa cell proliferation and inhibits apoptosis.
- CXCL12 regulates genes and proteins involved in the cell cycle and follicle development.
- CXCL12 activates the JAK/STAT signaling pathway via the CXCR4 receptor.

## Abstract

The ovary, as an important reproductive organ, tightly regulates the litter size of rabbits through its complex network of genes. This study aims to identify candidate genes related to litter size in rabbits through RNA sequencing and to analyze the regulatory effects of C-X-C motif chemokine ligand 12 (CXCL12) on granulosa cells (GCs).

This study used ovarian transcriptome sequencing to identify differentially expressed genes between the ovarian tissues of New Zealand female rabbits with high (H) and low (L) litter sizes. In addition, a new candidate gene which was highly expressed in group H, namely the chemokine ligand CXCL12, was selected for further verification of biological functions.

The cell counting kit-8 assay and flow cytometry analysis showed that CXCL12 can promote GCs proliferation but inhibit their apoptosis. Furthermore, quantitative reverse transcription polymerase chain reaction and western blotting indicated that CRABP1 regulated genes (PCNA, CCND1, CDK2, Bcl-2 and Bax) and proteins (CCND1, PCNA, Bcl-2 and Bax) related to cell cycle and cell proliferation. In addition, it can also regulate the expression levels of genes (TAF4B, CITED1, WNT2, WNT10B, and HSD17B1) and proteins (CITED1 and WNT10B) related to follicle development and litter size. Finally, it was found that CXCL12 targeted the CXCR4 receptor to activate the JAK/STAT signaling pathway.

We utilized bioinformatics to screen 184 genes potentially associated with litter size in New Zealand female rabbits. Among these, CXCL12 plays a role in regulating the expression of cell cycle-related genes, promoting GCs proliferation. As a result, CXCL12 emerges as a promising candidate marker for selecting high litter size female rabbits in future breeding and production practices.