Novel and Recurrent EBP Mutations in X-Linked Dominant Chondrodysplasia Punctata Shiro Ikegawa, 1,2 * Hirofumi Ohashi, 3 Tsutomu Ogata, 4 Akira Honda, 5 Masato Tsukahara, 6 Toshihide Kubo, 6 Mamori Kimizuka, 2 Masanori Shimode, 2,7 Tomonobu Hasegawa, 4 Gen Nishimura, 8 and Yusuke Nakamura 1 1 Laboratory of Genome Medicine, Human Genome Center, Institute of Medical Science, University of Tokyo, Tokyo, Japan 2 Department of Orthopedics, National Rehabilitation Center for Disabled Children, Tokyo, Japan 3 Division of Medical Genetics, Saitama Children’s Medical Center, Saitama, Japan 4 Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan 5 Department of Gastroenterology, University of Tsukuba, Ibaragi, Japan 6 School of Allied Health Sciences, Yamaguchi University, Yamaguchi, Japan 7 Department of Orthopaedics, NTT Kanto Medical Center, Tokyo, Japan 8 Department of Diagnostic Imaging, Nasu Central Hospital, Tochigi, Japan Chondrodysplasia punctata (CDP) is a het- erogeneous group of skeletal dysplasias characterized by stippled epiphyses. A sub- type of CDP, X-linked dominant chondro- dysplasia punctata (CDPX2), known also as Conradi-Hu ¨ nermann-Happle syndrome, is a rare skeletal dysplasia characterized by short stature, craniofacial defects, cata- racts, ichthyosis, coarse hair, and alopecia. The cause of CDPX2 was unknown until re- cent identification of mutations in the gene encoding  8 , 7 sterol isomerase emopamil- binding protein (EBP). Twelve different EBP mutations have been reported in 14 pa- tients with CDPX2 or unclassified CDP, but with no evidence of correlation between phenotype and nature of the mutation. To characterize additional mutations and in- vestigate possible phenotype-genotype cor- relation, we sequenced the entire EBP gene in 8 Japanese individuals with CDP; 5 of them presented with a CDPX2 phenotypes. We found EBP mutations in all 5 CDPX2 in- dividuals, but none in non-CDPX2 individu- als. Three of these CDPX2 individuals car- ried novel nonsense mutations in EBP and the other two, separate missense mutations that had been reported also in different eth- nic groups. Our results, combined with pre- vious information, suggest all EBP muta- tions that produce truncated proteins result in typical CDPX2, whereas the phenotypes resulted from missense mutations are not always typical for CDPX2. Patients with nonsense mutations showed abnormal ste- rol profiles consistent with a defect in  8 , 7 sterol isomerase. X-inactivation patterns of the patients showed no skewing, an obser- vation that supports the assumption that in- activation of the EBP gene occurs at random in affected individuals. Am. J. Med. Genet. 94:300–305, 2000. © 2000 Wiley-Liss, Inc. KEY WORDS: chondrodysplasia punctata; skeletal dysplasia; EBP muta- tion; X inactivation; steroid metabolism INTRODUCTION Chondrodysplasia punctata (CDP) refers to a hetero- geneous group of skeletal dysplasias characterized by stippled (punctate) epiphyses, including an X-linked recessive type (CDPX1, MIM 302950), an X-linked dominant type (CDPX2 or Conradi-Hu ¨ nermann- Happle syndrome, MIM 302960), a rhizomelic type (MIM 215100), a brachytelephalangic type (MIM 602497), a tibia-metacarpal type (MIM 118651), Zell- weger syndrome (MIM 21400); and other genetic and acquired disorders including Warfarin embryopathy [International Working Group on Constitutional Dis- eases of Bone, 1998]. The clinical manifestations of CDPX2 consist of skeletal abnormalities, cutaneous anomalies and cataracts. Skeletal abnormalities in- clude short stature, rhizomesomelic shortness of the limbs, deformity of the spine, and craniofacial defects Grant sponsor: Ministry of Education, Culture, Sports and Sci- ence of Japan; Grant number: 11470300. *Correspondence to: Shiro Ikegawa, M.D., Ph.D., Laboratory for Bone and Joint Diseases, SNP Research Center, RIKEN, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108- 8639, Japan. E-mail: sikegawa@ims.u-tokyo.ac.jp Received 27 January 2000; Accepted 9 April 2000 American Journal of Medical Genetics 94:300–305 (2000) © 2000 Wiley-Liss, Inc.