Mice lacking DUF1220 protein domains are hyperactive and show reduced fecundity

Sequences encoding DUF1220 protein domains show the most extreme human lineage-specific copy number increase of any coding region in the genome and have been linked to human brain evolution. In addition, DUF1220 copy number (dosage) has been implicated in influencing brain size within the human species, both in normal populations and in individuals associated with brain size pathologies (1q21-associated microcephaly and macrocephaly). More recently, increasing dosage of a subtype of DUF1220 has been linked with increasing severity of the primary symptoms of autism. Despite these intriguing associations, a function for these domains has not been described. As a first step in addressing this question we have developed the first transgenic model of DUF1220 function by removing the single DUF1220 domain (the ancestral form) encoded in the mouse genome. While resulting DUF1220-minus (KO) mice show no obvious anatomical peculiarities, they exhibit a significantly reduced fecundity (2= 19.1, df = 2, p = 7.0 x 10-5). Further extensive phenotypic analyses suggest that DUF1220 KO mice are hyperactive (p < 0.05) relative to wild type litter mates. The linking of DUF1220 loss to a hyperactive phenotype is consistent with separate findings in which DUF1220 over expression results in a down-regulation of mitochondrial function, suggesting a possible role in the prolongation of developmental processes (neoteny) that is most pronounced in the human lineage.

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