Original article 1 Mutation screening and association study of the UBE2H gene on chromosome 7q32 in autistic disorder Patrick Vourc’h a , Isabelle Martin a , Fre ´de ´ rique Bonnet-Brilhault b , Sylviane Marouillat a , Catherine Barthe ´le ´my b , Jean Pierre Mu ¨h a and Christian Andres a Autistic disorder is a severe neurodevelopmental disorder most probably caused by a complex interaction of genetic factors. Several genomewide scans identified multipoint LOD score peaks in region 7q32. In this region, UBE2H encodes an E2 enzyme of the ubiquitin-dependent pro- teolytic system. Mutations in another member of this system, the UBE3A gene, cause Angelman syndrome. The participation of E2 (ubiquitin-conjugating enzymes) or E3 (ubiquitin ligases) enzymes in neural development recently emerged. Given its physical location and function, we examined UBE2H as a candidate for involvement in autistic disorder. We confirmed by reverse transcription-polymer- ase chain reaction that the UBE2H gene was expressed in the rat and the human central nervous system. The rat UBE2H and human UBE2H deduced amino acid sequences are identical. We screened the seven exons of the UBE2H gene in autistic patients using single-strand conformation analysis. We observed a silent A-G transition at position 336. A case–control association study was performed using this A/G polymorphism. A significant association was found between the G allele and a subgroup of autistic patients with developmental quotient higher than 30 (P = 0.004). Although further studies are required, these results suggest that the UBE2H gene could be one of the 7q-susceptibility loci for autistic disorder. Psychiatr Genet 00:000–000  c 2003 Lippincott Williams & Wilkins. Psychiatric Genetics 2003, 00:000–000 Keywords: autistic disorder, UBE2H gene, mutation screening, single strand conformation polymorphism, association study a Ge ´ ne ´tique de la de ´ ficience mentale et de l’autisme, INSERM U316, Faculte ´ de Me ´decine, Tours, France and b Service Universitaire d’Explorations Fonctionnelles et Neurophysiologie en Pe ´ dopsychiatrie, INSERM U316, Ho ˆ pital Bretonneau, Tours, France. Sponsorship: France Telecom Foundation and Re ´ gion Centre supported this study. Correspondence and requests for reprints to Prof. Christian Andres, MD, PhD, INSERM U316, Faculte ´ de Me ´decine, 2bis, boulevard Tonnelle ´, 37032 Tours Cedex, France. E-mail: andres@med.univ-tours.fr Received 3 September 2002 Accepted 24 February 2003 Introduction Autistic disorder (MIM: 209850) is a severe neurodeve- lopmental disorder characterized by impairments in social interaction, deficits in communication, and restricted and stereotyped patterns of interests and behaviors (Rapin and Katzman, 1998). Twin and family studies have demonstrated that genetic factors are important in the etiology of autistic disorder (Bailey et al., 1995; Lord et al., 2000). The mode of inheritance is probably complex, with several genes interacting. The estimated number of genes implicated in autistic disorder ranges from three (Pickles et al., 1995) to 15 (Risch et al., 1999). Among all the genomewide scans performed in autistic disorder, some have identified multipoint LOD score peaks including region 7q32 (IMGSAC, 1998; Barrett et al., 1999; Philippe et al., 1999; Buxbaum et al., 2001; Liu et al. 2001; Shao et al., 2002). Chromosomal abnormalities in autistic patients have been reported in the 7q31-33 region (Ashley-Koch et al., 1999; Vincent et al., 2000; Warburton et al., 2000). Regarding the preferential transmission of paternal alleles, imprinting mutations have been suggested in autistic disorder (Ashley-Koch et al., 1999; IMGSAC, 2001). The region 7q32 contains imprinted genes (Hayashida et al., 2000). These observa- tions led to the suggestion of an autism susceptibility locus (AUTS1) on chromosome 7q. Considering the genetic complexity in autistic disorder, association studies of candidate genes in the region 7q32 may be more powerful than linkage studies (Piccardi et al., 2002). In light of this information, we searched for candidate genes in the 7q32 region. We chose the UBE2H gene (MIM: 601082) as a candidate gene in autistic disorder for the following reasons. First, this gene is located only 270 kb from the D7S530 marker linked to autistic disorder (IMGSAC, 1998). Second, UBE2H encodes an E2-enzyme of the ubiquitin-proteasome system, which catalyzes the covalent attachment of ubiquitin to target proteins for selective degradation (Kaiser et al., 1994). This proteolytic system is involved in several cellular functions, such as cell-cycle progression and regulation, DNA repair, signal transduction, synaptic plasticity and transcription (Hershko et al., 2000). Certain enzymes (E2 or E3 enzymes) from the ubiquitin-proteasome, like UbcR7 and Parkin, could play an important role in 0955-8829  c 2003 Lippincott Williams & Wilkins DOI: 10.1097/01.ypg.0000084946.07075.37 ED: susan Op: gopal/rajesh : lww_ypg_991093