Aberrant expression of imprinted genes and their regulatory network in cloned cattle

Domesticated animals cloned by somatic cell nuclear transfer (SCNT) generally have poor developmental competency, with many developmental abnormalities attributed to incomplete reprogramming of the nuclear genome and abnormal expression of genes important for regulation of growth and development. To investigate the molecular mechanism leading to the abnormalities of cloned animals, pathologic and histologic analyses were conducted on seven cloned cattle that were oversized at birth and had cardiac and pulmonary abnormalities. Quantitative reverse transcription (RT)-polymerase chain reaction (PCR) analysis of four imprinted genes IGF2, IGF2R, H19, and GRB10, as well as genes from related regulatory networks, were performed in liver, lung, kidney, and muscle to investigate disruption of expression. Expression of IGFBP2 was not detected in morphologically normal cloned cattle, but was detected in the liver, lung, kidney, and thymus of abnormal calves. Expression levels of IGF1 and imprinted genes IGF2 and H19 were substantially higher in these organs of abnormal cattle. In contrast, expression levels of GRB10, CTSD, and TRPV2 were substantially lower in abnormal cattle. Transcript abundance of IGFBP6 was higher in kidney, but lower in liver and lung. In conclusion, we inferred that altered expression of imprinted and related genes may be closely related to increased birth weight and pathologic changes in abnormal cloned cattle.