Increased prenatal @entity4864 expression due to the porcine intron3- XXXX mutation may be responsible for increased muscle mass.

@entity4865 @entity1707 @entity1184 @entity1373 @entity219 @entity70563 @entity70562 @entity4864
A SNP ( @entity4864 @entity4865 ) within intron 3 of disrupts a binding site for the repressor @entity219 finger BED-type containing 6 ( @entity70562 ), leading to increased carcass lean yields in @entity1707 . However, the relative contributions of prenatal as opposed to postnatal increased @entity4864 expression are unclear. As muscle fiber number is set at birth, prenatal and neonate skeletal muscle development is critical in determining mature growth potential. Therefore, the objectives of this study were to determine the contributions of @entity1373 and @entity1184 to increased muscle mass and to delineate the effect of the mutation on the expression of myogenic genes during prenatal and postnatal growth. Sows ( @entity4864 A/A) were bred to a single heterozygous ( @entity4864 A/G) boar. For fetal samples, sows were euthanized at 60 and 90 d of gestation (d60 and d90) to obtain fetuses. Male and female offspring were also euthanized at birth (0d), weaning (21d), and market weight of approximately 130 kg (176d). At each sampling time, the LM, psoas major (PM), and semitendinosus (ST) muscles were weighed. Samples of the LM were used to quantify the expression of IGF family members, myogenic regulatory factors (MRF), myosin heavy chain isoforms, and growth factors, myostatin, and . Liver samples were used to quantify and expression. At 176d, weights of LM, PM, and ST muscles were all increased approximately 8% to 14% (P < 0.01) in @entity1707 with paternal A (A(Pat)) alleles compared with those with paternal G (G(Pat)) alleles. Additionally, total muscle fiber number in the ST at 176d tended to be greater (P = 0.10), whereas muscle fiber cross-sectional area tended to be reduced ( P= 0.08) in A(Pat) @entity1707 compared with G(Pat) @entity1707 . In addition to the expected 2.7- to 4.5-fold increase (P  <= 0.02) in expression in the LM in A(Pat) compared with G(Pat) @entity1707 at postnatal sampling times (21d and 176d), @entity4864 expression was also increased (P  <= 0.06) 1.4- to 1.5-fold at d90 of gestation and at birth. At d90, expression of @entity70563 ( @entity70563 ), a MRF expressed in proliferating myoblasts, in the LM was greater (P = 0.01) in A (Pat) @entity1707 than in G(Pat) @entity1707 . Interestingly, at 21d hepatic expression was greater (P = 0.01), whereas expression decreased (P = 0.01) in A(Pat) @entity1707 compared with G(Pat) @entity1707 ; however, there were no differences (P >=  0.18) in hepatic expression between genotypes at 0d and 176d. These data suggest that prenatal @entity1373 of muscle fibers stimulated by increased @entity4864 expression may contribute to increased muscle mass of A(Pat) @entity1707 .
