HMG Advance Access published March 5, 2014 Human Molecular Genetics, 2014 1–7 doi:10.1093/hmg/ddu095 Respiratory failure, cleft palate and epilepsy in the mouse model of human Xq22.1 deletion syndrome Jian Zhou1, Ethan M. Goldberg2, N. Adrian Leu1, Lei Zhou2, Douglas A. Coulter2 and P. Jeremy Wang1,∗ 1Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, USA and 2The Children’s Hospital of Philadelphia, Division of Neurology, Colket Translational Research Building, 3501 Civic Center Boulevard, Philadelphia, PA 19104-4399, USA Downloaded from Received December 30, 2013; Revised and Accepted February 20, 2014 Chromosomal segmental deletion is a frequent cause of human diseases. A familial 1.1 Mb deletion of human chromosome Xq22.1 associates with epilepsy, cleft palate and developmental defects in heterozygous female http://hmg.oxfordjournals.org/ patients. Here, we describe a mouse mutant with a targeted deletion of the syntenic segment of the mouse X chromosome that phenocopies the human syndrome. Male mice with a deletion of a 1.1 Mb Nxf2–Nxf3 X- chromosomal segment exhibit respiratory failure, neonatal lethality and cleft palate. In female mice, heterozy- gosity for the deletion manifests cleft palate, early postnatal lethality, postnatal growth delay and spontaneous seizures in surviving animals, apparently due to X-chromosome inactivation. Furthermore, loss of a 0.35 Mb sub- region containing Armcx5, Gprasp1, Gprasp2 and Bhlhb9 is sufficient to cause the Xq22.1 syndrome phenotype. Our results support that the 1.1 Mb deletion of human Xq22.1 is the genetic cause of the associated syndrome. at University of Pennsylvania Libraries on April 8, 2014 INTRODUCTION section of Xq22.1 affected by the deletion contains 13 annotated genes, including NXF5. Mutations of this gene have been previ- Medical cytogenetics and array comparative genomic hybridiza- ously associated with mental retardation (4–6). A causal rela- tion (array-CGH) have identified a number of microdeletions of tionship between loss of the Xq22.1 region and phenotypic human chromosomes as common causes of genetic diseases. manifestations in human patients remains to be established and These regions of segmental deletions, usually a few mega the potential role of each of the 13 candidate genes remains to bases, often harbor multiple genes such that their loss could be determined. Here, we report the generation of mice with a lead to haploinsufficiency syndromes. The 22q11 deletion syn- 1.1 Mb deletion syntenic to the human Xq22.1 deletion. Mice drome (DiGeorge/velocardiofacial syndrome), caused by a with this deletion exhibit respiratory failure, cleft palate and epi- 3 Mb deletion, is the most common human microdeletion syn- lepsy, phenocopying the human syndrome. Deletion of a drome, occurring in 1:4000 live births (1, 2). Complementing 0.35 Mb subregion containing Armcx5, Gprasp1, Gprasp2 and studies of human patients, the generation of corresponding Bhlhb9 causes the same phenotype, identifying these as critical animal models can greatly facilitate the understanding of the candidate genes. pathogenesis of these complex syndromes, elucidate gene-to- phenotype relationships and identify causative genes. Genetic engineering of large chromosomal segmental deletions remains RESULTS challenging but has become increasingly feasible. Loss of a 1.1 Mb region of chromosome Xq22.1 is associated Respiratory failure and neonatal lethality in DelA/Y males with epilepsy, mental retardation and various developmental A 1.1 Mb region (Nxf2–Nxf3) on the mouse X chromosome is defects including cleft palate in heterozygous female patients syntenic to the 1.1 Mb region deleted in human patients with (3). The severity of symptoms differed between females affected the Xq22.1 syndrome (Fig. 1A). We previously generated a tar- by the deletion, and a male offspring of a heterozygous female geted allele [Del(XNxf2–Nxf3)1Jw] in which the Nxf2–Nxf3 died 15 days after birth due to a breathing failure. The 1.1 Mb segment is flanked by loxP sites (Fig. 1A) (7). We crossed ∗To whom correspondence should be addressed at: Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, USA. Tel: +1 2157460160; Fax: +1 2155735188; Email: [email protected] # The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected] 2 Human Molecular Genetics, 2014 Downloaded from http://hmg.oxfordjournals.org/ at University of Pennsylvania Libraries on April 8, 2014 Figure 1. Deletion mapping analysis of the critical interval on the X chromosome. (A) Schematic representation of the human Xq22.1 segment, the syntenic region on mouse X chromosome after targeted insertion of loxP sites, and the floxed and deletion alleles generated in this study. Dashed lines connect orthologous genes between mouse and human. Deletions on the mouse X chromosome (DelA, DelB and DelC; designated by dashed lines) were obtained by crossing mice carrying the respective floxed allele with Actb-Cre mice that ubiquitously express Cre recombinase (8). All loxP sites are in the same orientation, and in each deletion allele (deletion size indicated in brackets), only one loxP site is left. (B) Western blot analysis of GPRASP1/2 in DelA mutant brain at E16.5. (C) Western blot analysis of GPRASP1/2 in DelC mutant brain at E18.5. ACTB serves as a loading control. Note that the antibody recognizes both GPRASP1 and GPRASP2 (15). these mice with ubiquitously expressing Actb-Cre mice (8)to DelA/Y male pups examined developed asphyxia and died im- delete the 1.1 Mb Nxf2–Nxf3 segment, here referred to as mediately after delivery, indicating acute respiratory failure DelA (Fig. 1A). The DelA allele caused neonatal lethality in (Fig. 2A). all (DelA/Y) male pups. The observation that DelA/Y males Alveolarization, the formation of the alveolar gas exchange develop to term suggests that none of the 20 genes in the DelA unit, is one of the most critical steps during lung development, region are essential for early embryogenesis (Fig. 1A). and begins at E16.5 in the mouse (9). Histological analysis of Western blot analysis demonstrated absence of GPRASP1 and fetal stage (E16.5–E18.5) lungs (Fig. 2B–D) revealed no mor- GPRASP2 proteins (encoded by this region) in DelA/Y male phological difference between the lungs of wild-type (XY) and brain and reduced levels in DelA/+ female brain, indicating mutant (DelA/Y) mice at E16.5. However, from E17.5 that the deletion was complete (Fig. 1B). To determine the onward, lung development was significantly delayed in mutant cause of neonatal lethality in male mutant mice, we examined compared with wild-type mice. Wild-type lungs exhibited embryonic Day 18.5 (E18.5) embryos delivered by cesarean normal progression in the development of sac-like structures section. All wild-type E18.5 pups except one (13 of 14) breathed and septae. In contrast, mutant lungs developed less septation normally after delivery and were viable. However, all 11 E18.5 with thicker interstitial mesenchymal walls. Severe pulmonary Human Molecular Genetics, 2014 3 Downloaded from http://hmg.oxfordjournals.org/ Figure 3. Cleft palate in DelA/Y male embryos. (A) View of the palate from E18.5 wild-type and DelA/Y male embryos. (B and C) Hematoxylin and eosin stained coronal sections through the palate and oral cavity. Genotypes: WT, + /Y; DelA/Y, 2/Y. Abbreviations: c, cranial base; m, Meckel’s cartilage; nc, at University of Pennsylvania Libraries on April 8, 2014 nasal cavity; pp, primary palate; ps, palatal shelf; t, tongue. Table 1. Comparison of developmental defects among three mouse mutants with deletions in the syntenic region to human Xq22.1 Figure 2. Lung dysplasia in DelA/Y male embryos. (A) Asphyxia in E18.5 DelA/ Y male pups. Wild-type pups breathed normally. Pups were delivered at E18.5 by Deletion Respiratory Cleft palate Cleft palate Epilepsy in cesareansection.(B–D) Histological analysisof lungfromembryosatE16.5 (B), allele failure in 2/Y in 2/Y in +/2 +/2 females E17.5 (C) and E18.5 (D). Lung sections were stained with hematoxylin and eosin. neonates males females (handling) Genotypes: WT, +/Y; DelA/Y, 2/Y. (E18.5) (E18.5) DelA 11/11a 20/20 3/21 30/35 DelB None None None None hypoplasia may therefore account for the acute respiratory DelC 8/8 37/37 1/56 9/12 failure at birth in DelA/Y male embryos. aNumber of mice with the defect over the total number of mice examined. Cleft palate in DelA/Y males and DelA/1 females The palate separates the oral cavity from the nasal cavity and consists of the primary palate (bony hard plate) and the second- Partial postnatal lethality in juvenile DelA/1 females ary palate (muscular soft palate) (10). The secondary palate is formed by fusion of two palatal shelves. In the mouse, palatogen- All DelA/Y males died immediately after birth, whereas het- esis is initiated at E11.5 and fusion of the palatal shelves normal- erozygous DelA/+ females were viable at birth. However, ly completed by E15.5. At E18.5, all 20 DelA/Y male pups the majority of DelA/+ heterozygous females died post- displayed complete cleft palate (Fig. 3A). Palatal shelves were natally prior to weaning (Fig. 4A). We determined the survival formed in DelA/Y embryos at E13.5 (Fig. 3B), similar to those rate of DelA/+ females and wild-type female littermates. present in wild type. At E15.5, the palatal shelves were fused None of 31 wild-type females died during a 4-week observa- in wild-type embryos but remained separate without any sign tion period. In contrast, 45% (22 of 49) of DelA/+ viable of fusion in DelA/Y fetuses (Fig.