Differentially expressed genes in the femur cartilage transcriptome clarify the understanding of femoral head separation in chickens

Abstract

Locomotor problems are among one of the main concerns in the current poultry industry, causing major economic losses and affecting animal welfare. The most common bone anomalies in the femur are dyschondroplasia, femoral head separation (FHS), and bacterial chondronecrosis with osteomyelitis (BCO), also known as femoral head necrosis (FHN). The present study aimed to identify differentially expressed (DE) genes in the articular cartilage (AC) of normal and FHS-affected broilers by RNA-Seq analysis. In the transcriptome analysis, 12,169 genes were expressed in the femur AC. Of those, 107 genes were DE (FDR < 0.05) between normal and affected chickens, of which 9 were downregulated and 98 were upregulated in the affected broilers. In the gene-set enrichment analysis using the DE genes, 79 biological processes (BP) were identified and were grouped into 12 superclusters. The main BP found were involved in the response to biotic stimulus, gas transport, cellular activation, carbohydrate-derived catabolism, multi-organism regulation, immune system, muscle contraction, multi-organism process, cytolysis, leukocytes and cell adhesion. In this study, the first transcriptome analysis of the broilers femur articular cartilage was performed, and a set of candidate genes (AvBD1, AvBD2, ANK1, EPX, ADA, RHAG) that could trigger changes in the broiler´s femoral growth plate was identified. Moreover, these results could be helpful to better understand FHN in chickens and possibly in humans.

Downregulation of growth plate genes involved with the onset of femoral head separation in young broilers

“…FHS occurrence is also affected by broilers age, increasing at older ages ( Prisby et al, 2014 ). Our research group has been evaluating the FHS/FHN gene expression in several ages in femur ( Paludo et al, 2017 ; Hul et al, 2021 ; Goldoni et al, 2022 ; Santos et al, 2022 ) and in tibia ( Oliveira et al, 2020 ). In this way, trying to understand the genes more related with FHS onset, we have compared the common DE genes and also those exclusive to 21, 35, and 42 days of age in GP and AC.…”

“…Additionally, in order to verify the FHS gene expression profile among different ages, Ensembl IDs of DE genes identified in this study were compared with results from transcriptome studies of Peixoto et al (2019) , Oliveira et al (2020) , Hul et al (2021) and Goldoni et al (2022) . These studies evaluated early stages of FHS at 35 days in growth plate and articular cartilage ( Peixoto et al, 2019 ; Hul et al, 2021 ; Goldoni et al, 2022 ) and tibia head separation at 42 days of age ( Oliveira et al, 2020 ).…”

“…RNA sequences obtained in this study, as well as sequences from other GP and cartilage from normal and FHS-affected samples from our previous studies ( Peixoto et al, 2019 ; Oliveira et al, 2020 ; Hul et al, 2021 ; Goldoni et al, 2022 ) were used to verify the presence of variants involved with FHS. To this, sequences from femoral GP and AC of 35-day-old and tibia GP from 42-day-old broilers were downloaded from SRA database bioprojects # PRJNA352962, PRJNA350521, and PRJNA352716, respectively, totaling 24 samples (9 normal and 15 FHS-affected).…”

“…Over the years, global gene expression studies have provided a better understanding of the putative acting genes in the two tissues that are the primary sites of femoral head disorders. From transcriptomes of the femur articular cartilage (AC) and growth plate (GP) of 35-day-old broilers ( Peixoto et al, 2019 ; Hul et al, 2021 ; Goldoni et al, 2022 ), several candidate genes were prospected. Oliveira et al (2020) also pointed out that osteochondral downregulated genes are potentially triggering BCO in tibia of 42-day-old broilers.…”

“… Oliveira et al (2020) also pointed out that osteochondral downregulated genes are potentially triggering BCO in tibia of 42-day-old broilers. Most of the studies with FHN/FHS in chickens are focused on understanding the ossification processes and, generally, in animals older than 35 days of age ( Li et al, 2015 ; Paludo et al, 2017 ; Peixoto et al, 2019 ; Hul et al, 2021 ; Ramser et al, 2021 , 2022 ), since the highest incidences of this condition occur at these ages ( McNamee and Smyth, 2000 ; Paxton et al, 2014 ; Packialakshmi et al, 2015 ). Therefore, molecular mechanisms involved with femoral head separation in young age (21 days) broilers were identified using RNA sequencing, allowing highlighting genes and BP potentially related to the onset of this condition.…”