Ultrasonic vocalization impairment of Foxp2 (R552H) knockin mice related to speech-language disorder and abnormality of Purkinje cells

Abstract

Previous studies have demonstrated that mutation in the forkhead domain of the forkhead box P2 (FOXP2) protein (R553H) causes speech-language disorders. To further analyze FOXP2 function in speech learning, we generated a knockin (KI) mouse for Foxp2 (R552H) [Foxp2 (R552H)-KI], corresponding to the human FOXP2 (R553H) mutation, by homologous recombination. Homozygous Foxp2 (R552H)-KI mice showed reduced weight, immature development of the cerebellum with incompletely folded folia, Purkinje cells with poor dendritic arbors and less synaptophysin immunoreactivity, and achieved crisis stage for survival 3 weeks after birth. At postnatal day 10, these mice also showed severe ultrasonic vocalization (USV) and motor impairment, whereas the heterozygous Foxp2 (R552H)-KI mice exhibited modest impairments. Similar to the wild-type protein, Foxp2 (R552H) localized in the nuclei of the Purkinje cells and the thalamus, striatum, cortex, and hippocampus (CA1) neurons of the homozygous Foxp2 (R552H)-KI mice (postnatal day 10), and some of the neurons showed nuclear aggregates of Foxp2 (R552H). In addition to the immature development of the cerebellum, Foxp2 (R552H) nuclear aggregates may further compromise the function of the Purkinje cells and cerebral neurons of the homozygous mice, resulting in their death. In contrast, heterozygous Foxp2 (R552H)-KI mice, which showed modest impairment of USVs with different USV qualities and which did not exhibit nuclear aggregates, should provide insights into the common molecular mechanisms between the mouse USV and human speech learning and the relationship between the USV and motor neural systems.KE family ͉ nuclear aggregation ͉ autism ͉ endoplasmic reticulum stress T he phenotype of the speech-language disorder segregates as an autosomal dominant trait. The KE family consists of three generations in which approximately half of the members (15 members) have severe articulation difficulties accompanied by verbal and orofacial impairments. The speech difficulties cannot be fully attributed to the basic impairment of orofacial praxis; the affected KE members normally perform single simple oral movements but have trouble with language comprehension, including grammar as well as production (1-5). Recent studies in the KE family identified the forkhead box P2 (FOXP2) gene as the responsible genetic factor and found that a missense mutation (R553H) in the forkhead domain of FOXP2 cosegregates with the disorder in this family (2-5).In addition to a forkhead domain with a winged-helix DNA binding domain (6), FOXP2 also contains a glutamine-rich region (polyQ tract), zinc finger, and a leucine zipper motif for homodimerization and heterodimerization with Foxp1, 2, and 4 family members (7). FOXP2 also interacts with the C-terminal binding protein (CtBP) to act as a transcriptional repressor (7). The familial FOXP2 mutated protein (R553H) exhibits reduced DNA binding and defects in nuclear localization in vitro (8, 9). In addition, a nonsense mutation (R328X), another mutation related to the spe...

What can mice tell us about Foxp2 function?

“…Similar findings are also observed for compound heterozygotes that carry two different non-functional alleles on different gene copies [22 ]. In contrast, heterozygous mice survive to adulthood and appear overtly normal [22 ,24], although some studies have reported mild-to-moderate developmental delay [21,23] which might relate to differences in genomic background [25 ].…”

“…However, under conditions of elevated arousal (applying gentle pressure to the tail while lifting the animal) homozygotes do produce ultrasonic calls, albeit of lower intensity [22 ,54]. Pups that are heterozygous for loss-of-function Foxp2 alleles have been described as producing the same number of USIs as wild-types [22 ,54], or a reduced number [21,23]. Where fewer USIs were reported, developmental delay was also observed in the heterozygous state [21,23].…”

“…Data represent the mean of 84 and 141 Foxp2-positive cells taken from R552H and wild-type embryos respectively. Error bars indicate SEM and hat lead to a lack of Foxp2 protein (Foxp2-KO [21] or Foxp2-S321X [22 ]) and those that recapitulate the missense mutation found in the KE family (Foxp2-R552H-KI [23] or Foxp2-R552H-Enu (Figure 1, grey box) [22 ]). Homozygous mice that completely lack Foxp2, or that have only non-functional protein, are developmentally delayed and have severe motor impairments, dying at 3-4 weeks of age [21,22 ,23,24].…”

“…Pups that are heterozygous for loss-of-function Foxp2 alleles have been described as producing the same number of USIs as wild-types [22 ,54], or a reduced number [21,23]. Where fewer USIs were reported, developmental delay was also observed in the heterozygous state [21,23]. In-depth studies of heterozygotes carrying Foxp2 disruptions (Foxp2-S321X and Foxp2-R552H lines) did not detect major differences in the acoustic properties of USIs emitted by pups, as compared to wild-type littermates [54].…”

Devo-darwinismo : lo que el lenguaje nos enseña sobre el papel del desarrollo en la evolución natural

“…32 Sobre la inespecificidad funcional del lenguaje y su significado evolutivo véase Lorenzo (2007). 33 De hecho, otras variantes de FoxP2 han sido puestas en relación con otras habilidades y necesidades de los organismos portadores, como la comunicación ultrasónica que algunas especies de ratones emplean en la comunicación madre-hijo (Shu et al 2005, Fujita et al 2008) o la representación espacial mediante ecolocación de algunas especies de murciélagos (Li et al 2007). A falta de confirmación empírica, podría en todos los casos hablarse de habilidades basadas en la actividad de sistemas de computación homólogos.…”