Disruption of ST5 Is Associated with Mental Retardation and Multiple
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Downloaded from http://jmg.bmj.com/ on June 26, 2015 - Published by group.bmj.com Original article Disruption of ST5 is associated with mental retardation and multiple congenital anomalies Ina Go¨hring,1 Andreas Tagariello,1 Sabine Endele,1 Claus C Stolt,2 Michella Ghassibe´,3 Malcolm Fisher,4 Christian T Thiel,1 Udo Trautmann,1 Miikka Vikkula,3 Andreas Winterpacht,1 David R FitzPatrick,4 Anita Rauch1,5 1Institute of Human Genetics, ABSTRACT of expression of genes residing at the chromosomal Friedrich-Alexander University Background The authors observed a patient with breakpoints or in close proximity to them. In this Erlangen-Nuremberg, Erlangen, 2 a cryptic subtelomeric de novo balanced translocation 46, study, breakpoint mapping of a balanced de novo Germany Institute of Biochemistry, Emil-Fischer XY.ish t(11;20)(p15.4;q13.2) presenting with severe translocation t(11;20)(p15.4;q13.2) in a patient Centre, Friedrich-Alexander mental retardation, muscular hypotonia, seizures, bilateral with MR, seizures and multiple congenital anoma- University Erlangen-Nuremberg, sensorineural hearing loss, submucous cleft palate, lies led to the identification of ST5 (suppression of 3 Erlangen, Germany de Duve persistent ductus Botalli, unilateral cystic kidney dysplasia tumorigenicity 5; MIM 140750) as a novel gene for Institute, Universite´ catholique de Louvain, Brussels, Belgium and frequent infections. syndromic MR. 4Medical and Developmental Methods and Results Fluorescence in situ hybridisation Genetics Section, MRC Human mapping and sequencing of the translocation breakpoints METHODS Genetics Unit, Western General showed that no known genes are disrupted at 20q13.2 Fluorescence in situ hybridisation (FISH) Hospital, Edinburgh, UK and that ST5 (suppression of tumorigenicity 5; MIM Region-specific bacterial artificial chromosome 5Institute of Medical Genetics, University of Zurich, 140750) is disrupted on 11p15.4. By quantitative PCR (BAC) clones for FISH mapping were selected from Schwerzenbach-Zurich, from different human tissues, the authors found ST5 to be the NCBI and UCSC genome browsers (http:// Switzerland relatively evenly expressed in fetal tissues. ST5 www.ncbi.nlm.nih.gov, http:/genome.ucsc.edu/). expression was more pronounced in adult brain, kidney FISH analyses were performed using metaphase Correspondence to and muscle than in the corresponding fetal tissues, chromosomes prepared from lymphoblastoid cell Professor Anita Rauch, Institute fl of Medical Genetics, University whereas expression in other tissues was generally lower lines. Genomic BAC DNAs were uorescently of Zurich, Schorenstrasse 16, than in the fetal tissue. Using RNA in situ hybridisation in labelled with Cy3-dCTP (Amersham Biosciences, CH-8603 mouse, the authors found that St5 is expressed in the Freiberg, Germany) by standard nick translation Schwerzenbach-Zurich, frontal cortex during embryonic development. In adult with the DIG-Nick-Translation Kit (Roche, Basel, Switzerland; [email protected] mouse brain, expression of St5 was especially high in the Switzerland). The probes were blocked with Cot-1 hippocampal area and cerebellum. DNA to suppress repetitive sequences. Metaphase Received 26 May 2009 Conclusion Hence, the authors suppose that ST5 plays spreads were hybridised at 378C overnight with the Revised 10 September 2009 an important role in central nervous system development Cy3-labelled BAC probes and a specific FluoroX Accepted 10 September 2009 probably due to disturbance of DENN-domain-mediated (Amersham Biosciences)-labelled subtelomeric Published Online First 19 October 2009 vesicle formation and neurotransmitter trafficking. control probe (PAC probes GS-11q770-G7 or GS- Thus, these findings implicate ST5 in the aetiology of 20p1061-L1).2 After post-hybridisation washes, mental retardation, seizures and multiple congenital chromosomes were counterstained with 49,6- anomalies. diamidino-2-phenylindole (DAPI; Serva, Heidelberg, Germany). Images were captured on a Zeiss Axio- plan 2 microscope with a CCD camera and processed with the Isis Software (Metasystems. Altlussheim, Germany). INTRODUCTION Mental retardation (MR) is defined as a significant Long-template PCR and mini-FISH analyses impairment of cognitive and adaptive functions All long-template PCRs were performed with the with onset before age 18 years and affects about Expand Long Template PCR System (Roche Diag- 2e3% of the population. It occurs as an isolated nostics, Basel, Switzerland) according to the trait or as part of many syndromes, and, despite recommendations of the manufacturer with primer significant improvement in the identification of pairs chosen from the genomic sequence of the underlying causes, the majority of cases currently breakpoint-spanning BAC clones. Annealing remain without definitive diagnosis.1 Since MR is temperatures and elongation times were optimised extremely heterogeneous and occurs sporadically in for each primer pair. Purified long-template PCR most patients, identification of novel causative products (QIAquick PCR Purification Kit, Qiagen, genes by linkage analysis is difficult. In such cases, Hilden, Germany) were labelled with Cy3-dCTPs balanced chromosomal rearrangements, which by standard nick translation as described above, and occur in 0.6% of mentally retarded patients, are one FISH was performed on metaphase spreads. of the most promising sources for targeting partic- Hybridisation time was elongated to 48 h. ular genomic segments or genes responsible for MR or other developmental disorders in humans.1 The Breakpoint sequencing phenotypic effects observed in patients with truly Primer pairs for breakpoint-spanning PCRs were balanced chromosomal rearrangements can be chosen from the genomic sequence of the breakpoint- explained by the disruption of genes or by alteration containing segments on chromosomes 11 and 20. J Med Genet 2010;47:91e98. doi:10.1136/jmg.2009.069799 91 Downloaded from http://jmg.bmj.com/ on June 26, 2015 - Published by group.bmj.com Original article Figure 1 Subtelomeric screening and A cytogenetic analysis in our patient revealed a cryptic subtelomeric translocation with the karyotype 46,XY, t(11;20)(p15.4;q13.2). (A) Partial karyogram and ideogram. In addition, chromosome painting using libraries for chromosome 11 (green) and 20 (red) was performed (B). For mapping of the translocation breakpoints, fluorescence in situ hybridisation was performed with bacterial artificial chromosome (BAC) clones. BAC clones RP11- 152H18 (red) on chromosome 11 (with der(20) 20 11qter probe, green) (C) and RP5- der(11) 906P16 (red) on chromosome 20 (with 20 der(20) 11 20pter probe, green) (D) showed hybridisation signals localised on both derivative chromosomes, demonstrating that they spanned the breakpoint. 11 der(11) B C 11 D der(20) 20 der(11) der(20) der(11) Different combinations of forward and reverse primers were used Genotyping Console 3.0.2 software to call segments of copy- to amplify a breakpoint-spanning PCR product with the Expand number changes. 20 kbPlus (PCR System, dNTPack; Roche Diagnostics) according ST5 to the manufacturer’s recommendations. We amplified the Quantification of expression by real time reverse breakpoint-spanning PCR product from the derivative transcriptase (RT)-PCR chromosome 11 using the following primer pair Chr11-59- cDNAs were taken from the Human Fetal Multiple Tissue cDNA TCTTCTGCCTAATGGTCAGC-39 and Chr20-59-CTGCAAGC- (MTC) Panel and from the Human Adult Multiple Tissue cDNA CAAGAAGAGAGG-39. The breakpoint-spanning PCR product (MTC) Panel (Clontech, Mountain View, CA, USA). RT-PCR ST5 from the derivative chromosome 20 was generated with studies were performed as described previously using the pre- the primer pair Chr11-59-CCATCCATCTCTCCTCATTCCT- designed TaqMan Gene Expression Assay (Applied Biosystems; TAAGTT-39 and Chr20-59-CCAATTAAGATGAGAAGATCCC- Hs00373572_m1), and normalised against the mean of four 9 b b TCTAGGA-3 . Dye terminator cycle sequencing of the purified endogenous controls ( 2-microglobulin, -actin, hypoxanthine 3 PCR products was carried out using the DNA Sequencing Kit phosphoribosyltransferase 1 and RNA polymerase II). Relative ST5 BigDye-Terminator Cycle Sequencing Ready Reaction (Applied expression levels were compared with the mean value of Biosystems, Forster City, CA, USA). Sequencing products were expression in fetal brain. separated on an Applied Biosystems ABI3730 Sequencing System. RNA in situ hybridisation The NCBI BLAST program (http://ncbi.nlm.nih.gov/BLAST) and Murine expression of St5 was investigated on embryonic days the UCSC BLAT program (http://genome.ucsc.edu/cgi-bin/ 8.5, 13.5 and 15 (E8.5, E13.5, E15), in brain and kidneys of hgBlat) were used to analyse the sequencing files. newborn mice on days 6, 10 and 15 (P6, P10, P15) and in brains of 7-week-old mice and adult mice. Tissue was OCT (TissueTek, Copy-number analysis Sakura Finetek, Heppenheim, Germany) embedded and stored at To investigate the presence of the reported ST5 copy-number À808C. Serial cryostat sections at 10e12 mm were fixed in 4% variations in well-characterised control individuals, we paraformaldehyde/phosphate-buffered saline. A 448 bp mouse performed long-range PCR using intronic primers from intron 7 St5 riboprobe was generated by PCR using the primers to intron 10, which generated a 3.4 kb product in 192 healthy ggagactgtgggtcactactcc and aatatggtgaaggcagaagtgg and blood donors. Copy-number changes larger than 100 kb were subcloning of the amplicon into the pCR4-TOPO vector (Invi- investigated