Expression of NOL1/NOP2/sun domain (Nsun) RNA methyltransferase family genes in early mouse embryogenesis.

The NOL1/NOP2/sun domain-containing genes encode the RNA methyltransferases Nsun2, 3, 4, 5, 6 and 7. Methylated RNA pervades the transcriptome, yet the function of RNA methyltransferases is poorly understood. Nsun2 and Nsun4 participate in cell proliferation and differentiation, protein biosynthesis and cancer. In addition, Nsun2 and Nsun7 dysfunction might cause intellectual disability and male sterility, respectively. The functions of Nsun3, Nsun5 and Nsun6 are unknown. Given the widespread distribution of RNA methylation, it is possible that Nsun genes participate in a broader range of relevant biological processes including the regulation of embryogenesis. Here, we describe the expression pattern of Nsun genes during mouse embryo development. In situ hybridization showed developmentally regulated Nsun gene expression. Nsun genes express broadly during gastrulation, but enrich in specific tissues as embryogenesis proceeds. Nsun transcripts enrich in the developing brain, consistent with proposed functions in neurocognitive development. In addition, Nsun transcripts enrich in the developing ear, eye, olfactory epithelium, branchial arches, heart and limb, suggesting possible overlapping functions of NSUN proteins in neural, craniofacial, cardiac, and limb morphogenesis. Furthermore, Nsun2 and Nsun6 enrich in the caudal neural tube and newly formed somites, suggesting possible functions in body axis extension. These results suggest possible overlapping functions of NSUN proteins and RNA methylation in broad aspects of embryonic development.