Reduced home cage and social activity in Pou3f2⊿ mice.

Pou3f2/Brn2 is a transcription factor that helps to determine the cellular identity of neocortical or hypothalamic neurons. Mammalian Pou3f2 contains three homopolymeric amino acids that are not present in amphibian Pou3f2. These amino acids contribute to monoamine function, which may play specific roles in mammalian development and behavior.

Morphological change caused by loss of the taxon-specific polyalanine tract in Hoxd-13.

Sequence comparison of Hoxd-13 among vertebrates revealed the presence of taxon-specific polyalanine tracts in amniotes. To investigate their function at the organismal level, we replaced the wild-type Hoxd-13 gene with one lacking the 15-residue polyalanine tract by using homologous recombination. Sesamoid bone formation in knock-in mice was different from that in the wild type; this was observed not only in the homozygotes but also in the heterozygotes.