RESUMEN
We have sequenced a 1.1-Mb region of human chromosome 22q containing the dosage-sensitive gene(s) responsible for cat eye syndrome (CES) as well as the 450-kb homologous region on mouse chromosome 6. Fourteen putative genes were identified within or adjacent to the human CES critical region (CESCR), including three known genes (IL-17R, ATP6E, and BID) and nine novel genes, based on EST identity. Two putative genes (CECR3 and CECR9) were identified, in the absence of EST hits, by comparing segments of human and mouse genomic sequence around two solitary amplified exons, thus showing the utility of comparative genomic sequence analysis in identifying transcripts. Of the 14 genes, 10 were confirmed to be present in the mouse genomic sequence in the same order and orientation as in human. Absent from the mouse region of conserved synteny are CECR1, a promising CES candidate gene from the center of the contig, neighboring CECR4, and CECR7 and CECR8, which are located in the gene-poor proximal 400 kb of the contig. This latter proximal region, located approximately 1 Mb from the centromere, shows abundant duplicated gene fragments typical of pericentromeric DNA. The margin of this region also delineates the boundary of conserved synteny between the CESCR and mouse chromosome 6. Because the proximal CESCR appears abundant in duplicated segments and, therefore, is likely to be gene poor, we consider the putative genes identified in the distal CESCR to represent the majority of candidate genes for involvement in CES.
Asunto(s)
Anomalías Múltiples/genética , Centrómero/genética , Cromosomas Humanos Par 22/genética , Secuencia Conservada/genética , Anomalías Craneofaciales/genética , Anomalías del Ojo/genética , Ligamiento Genético , Cardiopatías Congénitas/genética , Animales , Exones/genética , Etiquetas de Secuencia Expresada , Humanos , Ratones , Técnicas de Amplificación de Ácido Nucleico , Mapeo Físico de Cromosoma , Ratas , Secuencias Repetitivas de Ácidos Nucleicos/genética , Homología de Secuencia de Ácido Nucleico , Síndrome , Transcripción GenéticaRESUMEN
Cat eye syndrome (CES) is a developmental disorder with multiple organ involvement, associated with the duplication of a 2-Mb region of 22q11.2. Using exon trapping and genomic sequence analysis, we have isolated and characterized a gene, CECR1, that maps to this critical region. The protein encoded by CECR1 is similar to previously identified novel growth factors: IDGF from Sarcophaga peregrina (flesh fly) and MDGF from Aplysia californica (sea hare). The CECR1 gene is alternatively spliced and expressed in numerous tissues, with most abundant expression in human adult heart, lung, lymphoblasts, and placenta as well as fetal lung, liver, and kidney. In situ hybridization of a human embryo shows specific expression in the outflow tract and atrium of the developing heart, the VII/VIII cranial nerve ganglion, and the notochord. The location of this gene in the CES critical region and its embryonic expression suggest that the overexpression of CECR1 may be responsible for at least some features of CES, particularly the heart defects.
Asunto(s)
Anomalías Múltiples/genética , Aberraciones Cromosómicas/genética , Cromosomas Humanos Par 22 , Sustancias de Crecimiento/genética , Péptidos y Proteínas de Señalización Intercelular , Adenosina Desaminasa , Adulto , Empalme Alternativo , Secuencia de Aminoácidos , Ano Imperforado/genética , Secuencia de Bases , Northern Blotting , Southern Blotting , Trastornos de los Cromosomas , Mapeo Cromosómico , Coloboma/genética , Feto/metabolismo , Sustancias de Crecimiento/metabolismo , Cardiopatías Congénitas/genética , Humanos , Hibridación in Situ , Proteínas de Insectos/genética , Datos de Secuencia Molecular , Especificidad de Órganos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Alineación de Secuencia , SíndromeRESUMEN
Duplication of a segment of the long arm of human chromosome 3 (3q26.3-q27) results in a syndrome characterized by multiple congenital abnormalities and neurological anomalies in some patients. We have identified a novel gene (KCNMB3) that maps to this region. KCNMB3 has significant sequence similarity to the regulatory subunit of the large-conductance calcium-activated potassium channel. Due to the significance of potassium channels in neuronal functions, the overexpression of this gene may play a role in the abnormal neurological functions seen in some of these patients. A related sequence corresponding to the second and third exons of this gene resides in the pericentromeric region of 22q11, where a number of other unprocessed pseudogenes are known to map.
Asunto(s)
Anomalías Múltiples/genética , Trastornos de los Cromosomas/genética , Cromosomas Humanos Par 22/genética , Cromosomas Humanos Par 3/genética , Duplicación de Gen , Genes , Proteínas del Tejido Nervioso/genética , Canales de Potasio Calcio-Activados , Canales de Potasio/genética , Secuencia de Aminoácidos , Secuencia de Bases , Trastornos de los Cromosomas/metabolismo , Exones/genética , Etiquetas de Secuencia Expresada , Femenino , Humanos , Hibridación Fluorescente in Situ , Transporte Iónico/genética , Subunidades beta de los Canales de Potasio de Gran Conductancia Activados por el Calcio , Masculino , Datos de Secuencia Molecular , Proteínas del Tejido Nervioso/fisiología , Reacción en Cadena de la Polimerasa , Potasio/metabolismo , Canales de Potasio/fisiología , Convulsiones/genética , Alineación de Secuencia , Homología de Secuencia de Aminoácido , SíndromeRESUMEN
Cat eye syndrome (CES) is associated with a duplication of a segment of human chromosome 22q11.2. Only one gene, ATP6E, has been previously mapped to this duplicated region. We now report the mapping of the human homologue of the apoptotic agonist Bid to human chromosome 22 near locus D22S57 in the CES region. Dosage analysis demonstrated that BID is located just distal to the CES region critical for the majority of malformations associated with the syndrome (CESCR), as previously defined by a single patient with an unusual supernumerary chromosome. However, BID remains a good candidate for involvement in CES-related mental impairment, and its overexpression may subtly add to the phenotype of CES patients. Our mapping of murine Bid confirms that the synteny of the CESCR and the 22q11 deletion syndrome critical region immediately telomeric on human chromosome 22 is not conserved in mice. Bid and adjacent gene Atp6e were found to map to mousechromosome 6, while the region homologous to the DGSCR is known to map to mouse chromosome 16.
Asunto(s)
Apoptosis/genética , Proteínas Portadoras/genética , Mapeo Cromosómico , Cromosomas Humanos Par 22/genética , Oftalmopatías/genética , Familia de Multigenes , Animales , Proteína Proapoptótica que Interacciona Mediante Dominios BH3 , Rotura Cromosómica/genética , Clonación Molecular , Dosificación de Gen , Marcadores Genéticos/genética , Humanos , Discapacidad Intelectual/genética , Ratones , Datos de Secuencia Molecular , Fenotipo , ARN Mensajero/metabolismo , Análisis de Secuencia de ADN , Células Tumorales CultivadasRESUMEN
The smallest region of deletion overlap in the patients we have studied defines a DIGeorge syndrome/velocardiofacial syndrome (DGS/VCFS) minimal critical region (MDGCR) of approximately 250 kb within 22q11. A de novo constitutional balanced translocation has been identified within the MDGCR. The patient has some features which have been reported in individuals with DGS/VCFS, including: facial dysmorphia, mental retardation, long slender digits and genital anomalies. We have cloned the breakpoint of his translocation and shown that it interrupts the clathrin heavy chain-like gene (CLTCL) within the MDGCR. The breakpoint of the translocation partner is in a repeated region telomeric to the rDNA cluster on chromosome 21p. Therefore, it is unlikely that the patient's findings are caused by interruption of sequences on 21p. The chromosome 22 breakpoint disrupts the 3' coding region of the CLTCL gene and leads to a truncated transcript, strongly suggesting a role for this gene in the features found in this patient. Further, the patient's partial DGS/VCFS phenotype suggests that additional features of DGS/VCFS may be attributed to other genes in the MDGCR. Thus, haploinsufficiency for more than one gene in the MDGCR may be etiologic for DGS/VCFS.
Asunto(s)
Anomalías Múltiples/genética , Cromosomas Humanos Par 21/genética , Cromosomas Humanos Par 22/genética , Clatrina/genética , Síndrome de DiGeorge/genética , Translocación Genética , Secuencia de Bases , Células Cultivadas , Preescolar , Mapeo Cromosómico , Cadenas Pesadas de Clatrina , Clonación Molecular , Anomalías Craneofaciales/genética , Cardiopatías Congénitas/genética , Humanos , Hibridación Fluorescente in Situ , Cariotipificación , Masculino , Datos de Secuencia Molecular , SíndromeRESUMEN
Cat eye syndrome (CES) is typically associated with a supernumerary bisatellited marker chromosome derived from human chromosome 22pter to 22q11.2. The region of 22q duplicated in the typical CES marker chromosome extends between the centromere and locus D22S36. We have constructed a long-range restriction map of this region using pulsed-field gel electrophoresis and probes to 10 loci (11 probes). The map covers -3.6 Mb. We have also used 15 loci to construct a yeast artificial chromosome contig, which encompasses about half of the region critical to the production of the CES phenotype (centromere to D22S57). Thus, the CES critical region has been mapped and a substantial portion of it cloned in preparation for the isolation of genes in this region.
Asunto(s)
Anomalías Múltiples/genética , Cromosomas Humanos Par 22 , Anomalías del Ojo/genética , Línea Celular , Cromosomas Artificiales de Levadura , Electroforesis en Gel de Campo Pulsado , Marcadores Genéticos , Humanos , Mapeo RestrictivoRESUMEN
Nonsense suppressors derived from Saccharomyces cerevisiae tRNA(Trp) genes have not been identified by classical genetic screens, although one can construct efficient amber (am) suppressors from them by making the appropriate anticodon mutation in vitro. Herein, a series of in vitro constructed putative suppressor genes was produced to test if pre-tRNA(Trp) processing difficulties could help to explain the lack of classical tRNA(Trp)-based suppressors. It is clear that inefficient processing of introns from precursor tRNA(Trp), or inaccurate overall processing, may explain why some of these constructs fail to promote nonsense suppression in vivo. However, deficient processing must be only one of the reasons why classical tRNA(Trp)-based suppressors have not been characterized, as suppression may still be extremely weak or absent in instances where the in vitro construct can lead to an accumulation of mature tRNA(Trp). Furthermore, suppression is also very weak in strains transformed with an intronless derivative of a putative tRNA(Trp) ochre (oc) suppressor gene, wherein intron removal cannot pose a problem.