Placental development in a mouse model of spinal muscular atrophy.

Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder, leading to fatal loss of motor neurons. It is caused by loss of function of the SMN gene, which is expressed throughout the body, and there is increasing evidence of dysfunction in non-neuronal tissues. Birthweight is one of most powerful prognostic factors for infants born with SMA, and intrauterine growth restriction is common. In the SMNΔ7 mouse model of SMA, pups with the disease lived 25% longer when their mothers were fed a higher fat, "breeder" diet. The placenta is responsible for transport of nutrients from mother to fetus, and is a major determinant of fetal growth. Thus, the present study tested the hypothesis that placental development is impaired in SMNΔ7 conceptuses. Detailed morphological characterization revealed no defects in SMNΔ7 placental development, and expression of key transcription factors regulating mouse placental development was unaffected. The intrauterine growth restriction observed in SMA infants likely does not result from impaired placental development.