Tissue Distribution, Gender- and Genotype-Dependent Expression of Autophagy-Related Genes in Avian Species

Abstract

As a result of the genetic selection of broiler (meat-type breeders) chickens for enhanced growth rate and lower feed conversion ratio, it has become necessary to restrict feed intake. When broilers are fed ad libitum, they would become obese and suffer from several health-related problems. A vital adaptation to starvation is autophagy, a self-eating mechanism for recycling cellular constituents. The autophagy pathway has witnessed dramatic growth in the last few years and extensively studied in yeast and mammals however, there is a paucity of information in avian (non-mammalian) species. Here we characterized several genes involved in autophagosome initiation and elongation in Red Jungle fowl (Gallus gallus) and Japanese quail (coturnix coturnix Japonica). Both complexes are ubiquitously expressed in chicken and quail tissues (liver, leg and breast muscle, brain, gizzard, intestine, heart, lung, kidney, adipose tissue, ovary and testis). Alignment analysis showed high similarity (50.7 to 91.5%) between chicken autophagy-related genes and their mammalian orthologs. Phylogenetic analysis demonstrated that the evolutionary relationship between autophagy genes is consistent with the consensus view of vertebrate evolution. Interestingly, the expression of autophagy-related genes is tissue- and gender- dependent. Furthermore, using two experimental male quail lines divergently selected over 40 generations for low (resistant, R) or high (sensitive, S) stress response, we found that the expression of most studied genes are higher in R compared to S line. Together our results indicate that the autophagy pathway is a key molecular signature exhibited gender specific differences and likely plays an important role in response to stress in avian species.

Muscle metabolism and atrophy: let’s talk about sex

“…Potential reasons or mechanism for this differential signaling during disuse have yet to be elucidated. While females tend to have less ubiquitinproteasome activity compared to males, females tend to have greater autophagy-related protein degradation compared to males [81,82]. Current literature suggests greater protein content of autophagy regulators of autophagy initiation and resolution compared to males [81,82], overall suggesting that males and females may preferentially favor different protein catabolic pathways.…”

“…Females tend to have less satellite cells [60,61], which may be partially mediated by testosterone-activation of ARs on the satellite cells [64][65][66]. Females also tend to have less basal ubiquitin-proteasome activity and greater autophagy activity compared to males [79][80][81][82]. Finally, females appear to have differential regulation of myostatin activity and subsequent alterations to muscle physiology [49,98].…”

Crosstalk between Autophagy and Obesity: Potential Use of Avian Model

“…Interestingly, we found that the expression of autophagy-related genes is tissueand gender-dependent. 47 For instance, it was found that hypothalamic Beclin1, UVRAC, Atg9a, Atg13, Atg4b, Atg7 and Atg5 mRNA levels were significantly higher in female compared to male chickens suggesting that hypothalamic autophagy might be involved in the regulation of feed intake. Recently, Kaushik and colleagues showed that autophagy regulates lipid metabolism within hypothalamic neurons which in turn modulate neuropeptide levels that control feed intake and energy homeostasis.…”

“…47 These genes are ubiquitously expressed and showed high similarity with their mammalian orthologs indicating that autophagy is a conserved mechanism in different species. Interestingly, we found that the expression of autophagy-related genes is tissueand gender-dependent.…”

“…48 Furthermore, using two experimental male quail lines divergently selected over 40 generations for low (resistant line) or high (sensitive line) stress response 49 it was found that the expression of several autophagy-related genes are higher in several tissues including adipose tissue in the resistant compared to the sensitive line. 47 Since autophagy has been shown to play a key role in stress response and fat metabolism and since the regulation of energy homeostasis and the stress response are coupled physiological processes, the differential expression of autophagy-related genes between the two quail lines indicated that these lines would be a very useful model to study the interaction between stress response, autophagy and fat metabolism.…”