The light response in chickens divergently selected for feather pecking behavior reveals mechanistic insights towards psychiatric disorders

Abstract

Background Feather pecking is a serious behavioral disorder in chickens that has a considerable impact on animal welfare and poses an economic burden for poultry farming. To study the underlying genetics of feather pecking animals were divergently selected for feather pecking over 15 generations based on estimated breeding values for the behavior. Methods and results By characterizing the transcriptomes of whole brains isolated from high and low feather pecking chickens in response to light stimulation we discovered a putative dysregulation of micro RNA processing caused by a lack of Dicer1. This results in a prominent downregulation of the GABRB2 gene and other GABA receptor transcripts, which might cause a constant high level of excitation in the brains of high feather pecking chickens. Moreover, our results point towards an increase in immune system-related transcripts that may be caused by higher interferon concentrations due to Dicer1 downregulation. Conclusion Based on our results, we conclude that feather pecking in chickens and schizophrenia in humans have numerous common features. For instance, a Dicer1 dependent disruption of miRNA biogenesis and the lack of GABRB2 expression have been linked to schizophrenia pathogenesis. Furthermore, disturbed circadian rhythms and dysregulation of genes involved in the immune system are common features of both conditions.

eQTL analysis of laying hens divergently selected for feather pecking identifies KLF14 as a potential key regulator for this behavioral disorder

“…Dystrophin deficient mice show an altered clustering of GABA A receptors ( Knuesel et al, 1999 ). We previously reported that mutations within or close to GABA receptors as well as differential expression of GABRA2 , GABRB2 , GABRE , and GABRG3 are associated with feather pecking ( Falker-Gieske et al, 2021 ). The central position of DMD in the gene-gene interaction network provides further evidence for our theory that feather pecking is a GABAergic dysfunction disorder [already discussed here ( Falker-Gieske et al, 2021 )].…”

“…We previously reported that mutations within or close to GABA receptors as well as differential expression of GABRA2 , GABRB2 , GABRE , and GABRG3 are associated with feather pecking ( Falker-Gieske et al, 2021 ). The central position of DMD in the gene-gene interaction network provides further evidence for our theory that feather pecking is a GABAergic dysfunction disorder [already discussed here ( Falker-Gieske et al, 2021 )]. A lack of GABA receptor expression has been linked to schizophrenia in humans [reviewed here ( Chiapponi et al, 2016 )].…”

“…Here the transcriptomic and phenotypic data from 167 chickens was analyzed through a comprehensive strategy combining expression quantitative trait loci (eQTL) mapping and the network analysis of gene-gene interactions to predict SNPs and regulatory pathways that had significant impacts on these abnormal behavior patterns. It is also hoped that the data presented here can be used as a possible model system for both obsessive-compulsive disorder and schizophrenia, due to the similarities of the disease ( Falker-Gieske et al, 2021 ). As such, further elucidating the pathways involved in FP could prove significant in explaining and understanding other mental disorders, not just in chickens.…”

“…There have been a number of studies undertaken to attempt to describe the underlying processes of FP, using gene expression analysis and mapping studies to link FP to immune response and multiple signaling pathways ( Wysocki et al, 2010 ; Haas and van der Eijk, 2018 ), with some studies linking FP to schizophrenia and obsessive-compulsive disorders, indicating its use as a potential model for these diseases ( Falker-Gieske et al, 2021 ). However, these studies have so far been unable to elucidate the exact mechanism for this feather pecking.…”

Hitchhiking of bactericidal/permeability-increasing protein-like gene with the fibromelanosis locus in Kadaknath black-bone-chicken

“…For instance, the feather pecking behavior of layers also occurs in Kadaknath and may result from introgression from commercial breeds. Interestingly, we identify gene flow between Kadaknath and commercial breeds at the GABRA2 (Gamma-aminobutyric acid type A receptor alpha2 subunit) locus, whose expression downregulation is associated with feather pecking in birds 59 . The intronic deletions that we identified in the GABRA2 locus, which occur in Kadaknath and commercial breeds, may be involved in regulating this gene.…”