# LncRNA RORB-IT1 Encoding a Micropeptide Regulates Progesterone Synthesis, Proliferation and Apoptosis in Chicken Granulosa Cells

## TL;DR

A new long non-coding RNA, RORB-IT1, and its micropeptide regulate progesterone, cell growth, and death in chicken egg cells, offering potential for improving poultry breeding.

## Contribution

Discovery of RORB-IT1, a bifunctional lncRNA/micropeptide that regulates granulosa cell function in chickens.

## Key findings

- RORB-IT1 is specifically expressed in chicken granulosa cells and promotes progesterone synthesis and cell proliferation.
- RORB-IT1 and its micropeptide have opposing effects on apoptosis, revealing a unique RNA–peptide balance mechanism.
- RORB-IT1 is upregulated by hormones like FSH, P4, and E2, and may improve egg-laying efficiency in poultry.

## Abstract

What are the main findings?
We identify RORB-IT1 as a novel lncRNA that is specifically expressed in chicken follicular granulosa cells and encodes a functional micropeptide, RORB-34aa.The RORB-IT1 RNA and its encoded RORB-34aa micropeptide synergistically promote progesterone synthesis and proliferation but have opposing effects on apoptosis, revealing a unique RNA–peptide balance mechanism.

We identify RORB-IT1 as a novel lncRNA that is specifically expressed in chicken follicular granulosa cells and encodes a functional micropeptide, RORB-34aa.

The RORB-IT1 RNA and its encoded RORB-34aa micropeptide synergistically promote progesterone synthesis and proliferation but have opposing effects on apoptosis, revealing a unique RNA–peptide balance mechanism.

What are the implications of the main findings?
This work expands the functional landscape of lncRNAs in avian reproduction by uncovering a bifunctional transcript that fine-tunes granulosa cell fate.RORB-IT1/RORB-34aa represents a potential genetic target for enhancing follicular development and egg-laying efficiency in poultry breeding.

This work expands the functional landscape of lncRNAs in avian reproduction by uncovering a bifunctional transcript that fine-tunes granulosa cell fate.

RORB-IT1/RORB-34aa represents a potential genetic target for enhancing follicular development and egg-laying efficiency in poultry breeding.

Ovarian follicular development determines the egg-laying performance in chickens. Besides hormonal signaling, epigenetic and post-transcriptional regulators, long non-coding RNAs (lncRNAs) also play a vital role in follicular development. We previously identified that RAR-related orphan receptor B-intronic transcript 1 (RORB-IT1), a novel lncRNA located in the intron of RORB, was differentially expressed in chicken pre-hierarchical and hierarchical follicular granulosa cells (Post-GCs). However, it remains unknown whether RORB-IT1 participates in regulating the development of chicken ovarian follicles. In this study, we further characterized the expression pattern of RORB-IT1 and explored its role in regulating the progesterone synthesis, proliferation and apoptosis of chicken Post-GCs. The results showed that RORB-IT1, with a full length of 383 bp, exhibits a uniform distribution in both the cytoplasm and nucleus of chicken Post-GCs. RORB-IT1 was specifically expressed in Post-GCs and upregulated by follicle-stimulating hormone (FSH), progesterone (P4) and estradiol (E2) in a dose-dependent manner. Functionally, RORB-IT1 promoted P4 synthesis and proliferation, while inhibiting the apoptosis of Post-GCs. Furthermore, we demonstrated that RORB-IT1 encoded a functional micropeptide exhibiting dual localization in both cytoplasmic and nuclear compartments. This micropeptide enhanced progesterone synthesis and proliferation, but paradoxically induced the apoptosis of Post-GCs when overexpressed independently. Collectively, this study uncovered the expression pattern and function of RORB-IT1 in chicken Post-GCs and provided a theoretical basis for improving the egg-laying performance in chickens.