Our results with the GENOTEND chip also confirm the negative correlation between DNAJA1 expression and the tenderness score [12], but for young bulls and steers of year 1 only, which confirms our hypothesis that some markers of beef quality are highly dependent on rearing practices and environmental conditions. DNAJA1 encodes a member of the large 40 kDa heat shock protein family (Hsp40). This protein is a co-chaperone of the 70 kDa heat shock protein (Hsp70) and is believed to play a role in protein folding and mitochondrial protein import. The DNAJA1/Hsp70 complex also directly
inhibits programmed cell death (or apoptosis), which supports the hypothesis of Ouali et al. [41] that apoptosis is important for the tenderization of beef during ageing. Depending on the animal group (young bulls or steers slaughtered year 1), DNAJB9,DNAJC3 or DNJAC10, which are also members of the Hsp40 family,were negatively correlated to tenderness scores (data not shown) just like DNAJA1, which supports the role of members of the Hsp40 family in tenderness. In humans,the DNAJ family has over 40 DNAJ members [48] and can be subdivided into three subfamilies: DNAJA proteins, DNAJB proteins and DNAJC proteins with different structural features. Our results also support the role
of some HspA (Hsp70), and some HspB (small HSPs) including Hsp27, in addition to that of DNAJA1 (Hsp40).
For instance, CRYAB, which encodes α B-crystallin and shares homology with Hsp27, was also negatively correlated with tenderness in steers. However, the precise genes of this family which are individually negatively correlated to tenderness scores depends on the animal