•    CRAG researchers have characterized the expression of more than 5000 new lncRNAs in the brain of the domestic goat, some of which undergo significant changes in their expression during the early stages of gestation.
•    The study highlights how the olfactory bulb and other brain regions undergo very pronounced changes in expression that could be related to adaptation to motherhood.
•    This knowledge is essential to understand the neurological mechanisms that regulate the development of maternal behaviour in ruminants.

Adaptation to motherhood is a complex process that involves significant changes in the maternal brain during pregnancy. In women, it has been found that pregnancy causes a loss of grey matter and a decrease in the thickness of the cerebral cortex, but that ventricular and cerebrospinal fluid volume increases, as well as the microstructural integrity of white matter. Recently, the research group led by CRAG researcher Marcel Amills has published a study that reveals how lncRNAs (long non-coding RNAs) undergo very important expression changes related to the brain remodelling process that triggers pregnancy in the domestic goat.

lncRNAs are a class of RNAs that do not code for proteins but have an essential role in regulating gene expression. Unlike mRNAs (messenger RNAs), which serve as templates for protein synthesis, lncRNAs have an exclusively regulatory function, influencing the transcription and translation of other genes, as well as chromatin modification. This regulatory capacity, although still insufficiently understood, makes lncRNAs fundamental in biological processes as complex as cell development or differentiation.

Changes in brain gene expression

In this study, CRAG researchers have extracted RNA from 12 regions of the brain of seven Murciano-Granadina goats, three of which were in their first month of gestation and have sequenced it at the National Centre for Genomic Analysis. Massive sequencing of RNAs present in a sample is a technique that provides a detailed view of the gene expression profile, allowing researchers to identify both protein-coding and non-coding genes. The results obtained with this technique indicate that the olfactory bulb, in particular, undergoes very significant changes in its lncRNA expression profile during this first stage of gestation compared to non-pregnant animals. In total, 238 lncRNAs were differentially expressed in the olfactory bulb, of which 155 were over-expressed and 83 under-expressed in pregnant goats, respectively. Other tissues, such as the pons, hippocampus, and frontal neocortex, also showed significant changes in lncRNA expression, but to a lesser extent.

The group led by researcher Marcel Amills is one of the first in the world to use RNA sequencing in brain tissues of domestic animals in order to find out the impact of pregnancy on gene expression patterns. The results of a previous study carried out by the same research group already showed that the olfactory bulb is one of the brain regions that undergoes the most changes in terms of mRNA gene expression, with 1207 differentially expressed genes, of which 381 are downregulated and 826 upregulated in pregnant goats. These alterations in the transcriptome discovered in both studies suggest that the brain of the pregnant goat undergoes very profound changes in gene expression patterns well before parturition, which probably contributes to facilitating the process of adaptation to motherhood. In fact, it is known that the elimination of the olfactory bulb in rodents causes pathological alterations of maternal behaviour, since often the mother does not build a nest and cannibalizes her progeny.

On the other hand, in this same study, more than 5000 lncRNAs that had not been previously described have been discovered. Although the specific function of these lncRNAs is still unknown, it can be anticipated that their function is related to the regulation of brain gene expression at the transcriptional, post-transcriptional and epigenetic levels. 

"lncRNAs are often defined as the dark matter of the genome since practically nothing is known about their specific functions and the identities of the genes they regulate. All this constitutes a challenge of the first magnitude since the repertoire of lncRNAs is mostly species-specific and, therefore, we cannot make inferences about the functions of lncRNAs in domestic animals from the results obtained in other species" says Marcel Amills.

Implications for gestation biology in mammals

As a next step, it is planned to carry out studies on the structure and use of the transcripts to obtain a much deeper insight into the changes that pregnancy triggers in the brain of the pregnant goat.

This research not only significantly expands the knowledge about the ruminant lncRNA catalogue, but also provides valuable information to study the molecular basis of maternal behaviour development in the domestic goat. Results such as these show the usefulness of domestic animals as a model to study the biology of gestation and understand how alterations in brain gene expression can affect the establishment of an emotional bond between the mother and her offspring.

Reference Article

Endika Varela-Martínez, María Gracia Luigi-Sierra, Dailu Guan, Manel López-Béjar, Encarna Casas, Sergi Olvera-Maneu, Jaume Gardela, Maria Jesús Palomo, Uchebuchi Ike Osuagwuh, Uchechi Linda Ohaneje, Emilio Mármol-Sánchez, and Marcel Amills. The landscape of long noncoding RNA expression in the goat brain. Journal of Dairy Science, https://doi.org/10.3168/jds.2023-23966

About the authors and funding of the study

This research was supported by grant PID2019-105805RB-I00 funded by MCIN/AEI/10.13039/501100011033, by grant PID2022-136834OB-I00 funded by MCIIN/AEI/10.13039/501100011033, and by the European Regional Development Fund (ERDF; A way of making Europe). We also acknowledge the support of the Centres de Recerca de Catalunya (CERCA) program of the Generalitat de Catalunya (Barcelona, Spain) and the Center of Excellence Severo Ochoa 2020–2023 (Barcelona, Spain; CEX2019–000902-S) grant funded by MCIN/AEI/10.13039/501100011033 and awarded to the Centre for Research in Agricultural Genomics (CRAG; Bellaterra, Spain). Endika Varela-Martínez is recipient of a Margarita Salas grant for the training of young doctors (MARSA21/83) financed by the NextGenerationEU funds of the European Union through the plan for recovery, transformation, and resilience of the Ministerio de Universidades (Madrid, Spain). María Luigi-Sierra was funded with a PhD fellowship (Formación de Personal Investigador; BES-2017-079709) awarded by the Ministerio de Economía y Competitividad (Madrid, Spain). Dailu Guan was supported by a PhD fellowship from the China Scholarship Council (Ministry of Education, Beijing, China). Emilio Mármol-Sánchez was funded with a PhD fellowship (FPU15/01733) awarded by the Ministerio de Educación y Cultura (Madrid, Spain). RNA sequencing data have been deposited in the Sequence Read Archive (https://www.ncbi.nlm.nih.gov/sra) under the Bioproject accession number PRJNA808876. Data about novel lncRNAs identified in this study are available in a supplementary file (Supplemental Table S2). Supplemental material for this article is available at https://figshare.com/s/893e50eddaddd8b6635c. The slaughtering protocol was approved by the Ethics Committee on Animal and Human Experimentation of the Universitat Autònoma de Barcelona (project approval code CEEAH: 4790). The authors have not stated any conflicts of interest.