article 116 nature genetics • volume 32 • september 2002 Targeted mutation of Cyln2 in the Williams syndrome critical region links CLIP-115 haploinsufficiency to neurodevelopmental abnormalities in mice Casper C. Hoogenraad 1,2 , Bas Koekkoek 2 , Anna Akhmanova 1 , Harm Krugers 3 , Bjorn Dortland 1 , Marja Miedema 1 , Arjan van Alphen 2 , Werner M. Kistler 2 , Martine Jaegle 1 , Manoussos Koutsourakis 1 , Nadja Van Camp 4 , Marleen Verhoye 4 , Annemie van der Linden 4 , Irina Kaverina 5 , Frank Grosveld 1 , Chris I. De Zeeuw 2 & Niels Galjart 1 Published online: 26 August 2002, doi:10.1038/ng954 Williams syndrome is a neurodevelopmental disorder caused by the hemizygous deletion of 1.6 Mb on human chromosome 7q11.23. This region comprises the gene CYLN2, encoding CLIP-115, a microtubule-binding protein of 115 kD. Using a gene-targeting approach, we provide evidence that mice with haploinsufficiency for Cyln2 have features reminiscent of Williams syndrome, including mild growth deficiency, brain abnormalities, hippocampal dysfunction and particular deficits in motor coordination. Absence of CLIP-115 also leads to increased levels of CLIP-170 (a closely related cytoplasmic linker protein) and dynactin at the tips of growing microtubules. This pro- tein redistribution may affect dynein motor regulation and, together with the loss of CLIP-115–specific functions, underlie neurological alterations in Williams syndrome. 1 MGC Department of Cell Biology and Genetics, Erasmus University, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands. 2 MGC Department of Neuroscience, Erasmus University, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands. 3 Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands. 4 Bio-Imaging Lab, University of Antwerp (RUCA), Belgium. 5 Institute of Molecular Biology, Austrian Academy of Sciences, Salzburg, Austria. Correspondence should be addressed to N.G. (e-mail: galjart@ch1.fgg.eur.nl) or C.I.D.Z. (e-mail: dezeeuw@anat.fgg.eur.nl). Introduction Williams (or Williams-Beuren) syndrome (OMIM 194050) is a rare neurodevelopmental disorder, with an incidence of 1 in 20,000. It is characterized by cardiovascular abnormalities (par- ticularly supravalvular aortic stenosis, SVAS), transient juvenile hypercalcemia, abnormal weight gain and growth, and unusual facial features 1 . In addition, individuals with Williams syndrome generally have a unique neurological and behavioral profile 2 . Affected individuals have poor spatial cognition, but have notably intact language and musical abilities and relatively strong face-processing ability. Although they are not ataxic, individuals with Williams syndrome have coordination problems that are particularly obvious in walking up or down a staircase. Affected individuals are highly sensitive to certain classes of sounds, and have IQs in the mild to moderate range of mental retardation. Other characteristic behaviors include a friendly, outgoing per- sonality and an apparent lack of fear. Williams syndrome is caused by the hemizygous deletion of a region of approximately 1.6 Mb (the Williams syndrome critical region, or WSCR) of chromosome band 7q11.23 (ref. 3). The WSCR contains at least 17 genes, including those encoding syn- taxin 1A (STX1A), elastin (ELN), LIM kinase 1 (LIMK1) and CLIP-115 (CYLN2). The region is bordered by repeats, leading to the hypothesis that Williams syndrome is caused by illegitimate homologous recombination at the repeats during meiosis. Affected individuals carrying minor deletions that span only part of the WSCR 4 have been identified, however. Study of these indi- viduals and of affected individuals with point mutations has established that haploinsufficiency for ELN is linked to cardiovas- cular abnormalities in Williams syndrome, particularly SVAS 5,6 . It has also been suggested that insufficiency of LIM kinase 1 results in visuo-spatial cognition problems 7 , although more recent stud- ies have not verified this hypothesis 8 . Therefore, although defi- ciency in LIMK1 may contribute to part of the cognitive problems in Williams syndrome, it is now thought that other genes are responsible for most of the behavioral abnormalities associated with Williams syndrome. Deletion mapping in individuals with partial phenotypes and atypical deletions indicates that these genes are probably located in a region telomeric to RFC2 that con- tains the CYLN2, GTF2IRD1 and GTF2I loci 3,4,8 . We have cloned the cDNA encoding CLIP-115, which is most abundantly expressed in dendrites and cell bodies of many neu- rons in the brain 9 . Both CLIP-115 and CLIP-170 belong to a group of proteins that specifically associate with the ends of growing microtubules 10,11 . These proteins are believed to have distinct roles in regulating microtubule dynamics and in establishing interac- tions between microtubule tips and various cellular structures, including cargoes destined for microtubule-based, minus- end–directed transport by dynein. In line with this view, both CLIPs interact with CLASPs, which are proteins involved in the © 2002 Nature Publishing Group http://www.nature.com/naturegenetics