Histone H3 Threonine Phosphorylation Regulates Asymmetric Histone Inheritance in the Drosophila Male Germline.

A long-standing question concerns how stem cells maintain their identity through multiple divisions. Previously, we reported that pre-existing and newly synthesized histone H3 are asymmetrically distributed during Drosophila male germline stem cell (GSC) asymmetric division. Here, we show that phosphorylation at threonine 3 of H3 (H3T3P) distinguishes pre-existing versus newly synthesized H3. Converting T3 to the unphosphorylatable residue alanine (H3T3A) or to the phosphomimetic aspartate (H3T3D) disrupts asymmetric H3 inheritance. Expression of H3T3A or H3T3D specifically in early-stage germline also leads to cellular defects, including GSC loss and germline tumors. Finally, compromising the activity of the H3T3 kinase Haspin enhances the H3T3A but suppresses the H3T3D phenotypes. These studies demonstrate that H3T3P distinguishes sister chromatids enriched with distinct pools of H3 in order to coordinate asymmetric segregation of "old" H3 into GSCs and that tight regulation of H3T3 phosphorylation is required for male germline activity.

Asymmetric crying facies in the 22q11.2 deletion syndrome: implications for future screening.

OBJECTIVE: Asymmetric crying facies (ACF) is congenital hypoplasia of the depressor anguli oris muscle characterized by asymmetry of lower lip depression during crying. This has an overall incidence of 0.6%. This study determines the incidence of ACF in a large population of patients with 22q11.2 deletion. PATIENTS AND METHODS: A retrospective review of medical records on patients with a confirmed 22q11.2 deletion was undertaken. RESULTS: A total of 836 records were reviewed. Of these, 117 (14%) were noted to have ACF on physical examination. Within this latter group, palatal anomalies were common (77%), as was congenital heart disease (78%); however, these numbers did not differ significantly from their known prevalence in the 22q11.2 population. CONCLUSIONS: We report a 14% incidence of ACF in patients with a 22q11.2 deletion, significantly higher than in the general population. We suggest, therefore, that newborns with ACF be referred for further screening for the 22q11.2 deletion syndrome.