RNA-binding protein. Binds poly(G) and poly(U) but not poly(A) or poly(C). Regulates somite formation, probably by regulating gene expression (By similarity). Nuclear very early in embryonic development (at two hours post-fertilization), becoming cytoplasmic in later embryonic stages through to adulthood. Shows tissue-specific expression during embryonic development. At stage 23, expressed preferentially in structures that will develop into muscle (mesodermal) and neural (ectodermal) tissue. From stage 37 onwards, highly expressed in neurons and skeletal muscle tissue. Expression remains tissue-specific in adults, being localized to neurons of the central nervous system (CNS), all spermatogenic cells of the testis and skeletal muscle. Within skeletal muscle, expression appears to be localized to costameres. The tandem Agenet-like domains preferentially recognize trimethylated histone peptides. Belongs to the FMR1 family. Contaminating sequence. Sequence of unknown origin in the C-terminal part.