The Turner syndrome-associated neurocognitive phenotype maps to distal Xp

Abstract

Turner syndrome (TS) is associated with a characteristic neurocognitive profile that includes impaired visuospatial/perceptual abilities. We used a molecular approach to identify a critical region of the X chromosome for neurocognitive aspects of TS. Partial deletions of Xp in 34 females were mapped by FISH or by loss of heterozygosity of polymorphic markers. Discriminant function analysis optimally identified the TS-associated neurocognitive phenotype. Only subjects missing approximately 10 Mb of distal Xp manifested the specified neurocognitive profile. The phenotype was seen with either paternally or maternally inherited deletions and with either complete or incomplete skewing of X inactivation. Fine mapping of informative deletions implicated a critical region of <2 Mb within the pseudoautosomal region (PAR1). We conclude that haploinsufficiency of PAR1 gene(s) is the basis for susceptibility to the TS neurocognitive phenotype.

Figure 1

Mapping of subjects with nonmosaic Xp deletions. Related subjects are indicated. Bars indicate regions present. Shaded bars indicate subjects with TS neurocognitive phenotype. Approximate physical distances are shown on the left. Deletions are grouped according to results of FISH, with markers shown on the right; order of subjects within groups is arbitrary.

Figure 2

The neurocognitive phenotype maps to distal Xp. Data for deletion mapping, X inactivation, parent of origin (p = paternal, m = maternal), and neurocognitive phenotype are shown for the eight subjects with the smallest terminal deletions and for two subjects with interstitial deletions (fig. 1). Black lines indicate regions not deleted; gray lines indicate uncertainty. Underscored subjects indicate mother-daughter pairs; double-underscored subjects indicate mz twins.