Biomedical subjects

E A Lindsay

Publications and source records attributed to E A Lindsay.

At least 19 recordsLinked to original sources

PubMed1998

Congenital heart defects and 22q11 deletions: which genes count?

Hemizygous deletions on the long arm of chromosome 22 (del22q11) are a relatively common cause of congenital heart disease. For some specific heart defects such as interrupted aortic arch type B and tetralogy of Fallot with absent pulmonary valve, del22q11 is probably the most frequent genetic cause. Although extensive gene searches have been successful in discovering many novel genes in the deleted segment, standard positional cloning has so far failed to demonstrate a role for any of these genes in the disease. We show how the use of experimental animal models is beginning to provide an insight into the developmental role of some of these genes, while novel genome manipulation technologies promise to dissect the genetic aspects of this complex syndrome.

Animals↗

PubMed1998

Functional analysis of Gscl in the pathogenesis of the DiGeorge and velocardiofacial syndromes.

Gscl encodes a Goosecoid-related homeodomain protein that is expressed during mouse embryogenesis. In situ hybridization and immunohistochemistry studies show that Gscl is expressed in the pons region of the developing central nervous system and primordial germ cells. Gscl expression is also detected in a subset of adult tissues, including brain, eye, thymus, thyroid region, stomach, bladder and testis. Gscl is located within a region of the mouse genome that is syntenic with the region commonly deleted in DiGeorge and velocardiofacial syndrome (DGS/VCFS) patients. DGS/VCFS patients have craniofacial abnormalities, cardiac outflow defects and hypoplasia of the parathyroid gland and thymus due to haploinsufficiency of a gene or genes located within the deleted region. Thus, the genomic location of Gscl and its expression in a subset of the tissues affected in DGS/VCFS patients suggest that Gscl may contribute to the pathogenesis of DGS/VCFS. To determine the role of Gscl during mouse embryogenesis and in DGS/VCFS, we have deleted Gscl by gene targeting in mouse embryonic stem cells. Both Gscl heterozygous and Gscl null mice were normal and fertile, suggesting that Gscl is not a major factor in DGS/VCFS. Interestingly, expression of the adjacent Es2 gene in the pons region of Gscl null fetuses was absent, suggesting that mutations within the DGS/VCFS region can influence expression of adjacent genes. In addition, embryos that lacked both Gscl and the related Gsc gene appeared normal. These studies represent the first functional analysis of a DGS/VCFS candidate gene in vivo. These Gscl null mice will be an important genetic resource for crosses with other mouse models of the DGS/VCFS.

Abnormalities, Multiple↗

PubMed1998

ES2, a gene deleted in DiGeorge syndrome, encodes a nuclear protein and is expressed during early mouse development, where it shares an expression domain with a Goosecoid-like gene.

ES2 is a gene deleted in DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS) which has homologs in species as distant as Caenorhabditis elegans and Drosophila . The function of ES2 is unknown, and the predicted protein sequence does not contain motifs which suggest a particular role in the developmental defects present in DGS and VCFS. Here we show that the mouse homolog, Es2 , is transcribed in two forms resulting from the use of alternative polyadenylation signals. Structural analysis programs predict that the Es2 -encoded peptide has a coiled-coil domain, and transfection experiments with an Es2 -green fluorescent protein (GFP) fusion construct show that the peptide is recruited into the nucleus. Es2 is highly expressed during mouse embryogenesis from E7 onwards. In situ hybridization with an RNA probe revealed that the gene is widely expressed; however, relatively higher expression was detected in the nervous system, with a particularly high area of expression in a sub-region of the pons. The Es2 expression domain in the pons is shared with a Goosecoid-like gene ( Gscl) which is located upstream of Es2 , and raises the possibility that the two genes share regulatory elements and/or interact in this region of the developing brain. This finding suggests that different genes in the deleted region may be functionally related and might explain the occurrence of the characteristic phenotype in patients with non-overlapping genetic lesions.

Amino Acid Sequence↗

PubMed1997

Deletion of chromosome 22q11 and pseudohypoparathyroidism.

A newborn boy with complex congenital heart disease, unilateral renal agenesis, and hypocalcemia was found to have a submicroscopic deletion of 22q11.2 (DiGeorge anomaly). In evaluating the pathogenesis of the hypocalcemia, repeatedly elevated or normal levels of parathyroid hormone were found, consistent with a diagnosis of pseudohypoparathyroidism. Pseudohypoparathyroidism can be due to mutation of a GTP binding protein (Gs-alpha protein) located on chromosome 20. Since there is another G protein locus (Gz alpha) adjacent to the DiGeorge critical region of chromosome 22, we hypothesized that a more extensive deletion may lead to pseudohypoparathyroidism. Fluorescence in situ hybridization was performed using a probe containing the Gz alpha gene, but no deletion was detected. This patient emphasizes the importance of determining the pathogenesis of the hypocalcemia in cases of DiGeorge anomaly.

Chromosome Deletion↗

PubMed1997

A genetic etiology for interruption of the aortic arch type B.

Interrupted aortic arch (IAA) type B is a congenital heart defect believed to be caused by an anomaly of bronchial arch mesenchymal development. IAA type B has been associated with DiGeorge syndrome (DGS), which includes conotruncal heart defects, T-cell immunodeficiency, hypocalcemia, and facial abnormalities. The great majority of DGS cases are associated with hemizygous deletions at the chromosome 22q11 locus. The present study was designed to establish the involvement of the 22q11 locus in the etiology of IAA type B, independently from the typical DGS phenotype. An evaluation was performed on 73 patients with conotruncal heart defects using fluorescence in situ hybridization (FISH) analysis with probes from the 22q11 DGS locus. From this group, 7 patients were deleted (including 4 of the 11 patients with IAA type B). FISH analysis was extended to a total of 22 patients with IAA type B and 11 of these (50%) were deleted. FISH and Southern blot analyses using additional markers within the DiGeorge chromosomal region were performed on patients found not to be deleted in the initial FISH screening. No small deletions or rearrangements were detected. In our patient population, a single, specific genetic defect is the basis for one half of the IAA type B cases. These data suggest that IAA type B is one of the most etiologically homogeneous congenital heart defects. A 22q11 deletion in IAA type B may or may not be associated with the typical DGS phenotype. Therefore, IAA type B, per se, should be an indication for 22q11 deletion testing.

Aorta, Thoracic↗

PubMed1997

Comparative mapping of the DiGeorge syndrome region in mouse shows inconsistent gene order and differential degree of gene conservation.

We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial (VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions (distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved; only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a mouse model for the 22q11 deletion with chromosome engineering technologies.

Animals↗

PubMed1997

Tobacco control activities of primary-care physicians in the Community Intervention Trial for Smoking Cessation. COMMIT Research Group.

OBJECTIVE: To compare tobacco control practices of physicians and their staff in Intervention communities with those in Comparison communities of the Community Intervention Trial for Smoking Cessation (COMMIT). DESIGN: COMMIT was a randomised trial testing community-based intervention for smoking cessation carried out over four years. SETTING: Eleven matched pairs of communities assigned randomly to Intervention and Comparison conditions. PARTICIPANTS AND INTERVENTIONS: Physicians in the Intervention communities participated in continuing medical education (CME). Training for office staff focused on tobacco control and office intervention "systems". OUTCOME MEASURES: Smoking control attitudes and practices reported by primary-care physicians in the 22 communities, smoking policies, and practices of 30 randomly selected medical offices in each community, and patient reports of physician intervention activities. RESULTS: Response rates to the physicians' mail survey were 45% and 42% in Intervention and Comparison communities, respectively. Telephone interviews of office staff had response rates of 84% in both conditions. Physicians in Intervention communities were more likely to attend training than those in Comparison communities (53% and 26%, respectively (P<0.0005)). In both conditions, training attendees perceived themselves as being better prepared to counsel smokers than non-attendees (P < or = 0.01) and reported more activity in smoking intervention. Intervention communities carried out more office-based tobacco control activities (P = 0.002). Smokers in Intervention communities were more likely to report receiving reading material about smoking from their physicians (P = 0.026). No other differences in physician intervention activities were reported by smokers between the Intervention and Comparison communities. CONCLUSIONS: The COMMIT intervention had a significant effect on some reported physician behaviours, office practices, and policies. However, most physicians still did not use state-of-the-art smoking intervention practices with their patients and there was little, or no, difference between patient reports of intervention activities of physicians in the Intervention and Comparison communities. Better systems and incentives are needed to attract physicians and their staff to CME and to encourage them to follow through on what they learn. The recently released Agency for Health Care Policy and Research clinical practice guideline for smoking cessation and other standards and policies outline these systems and offer suggestions for incentives to facilitate adoption of these practices by physicians.

Adult↗

PubMed1997

A mouse gene (Dgcr6) related to the Drosophila gonadal gene is expressed in early embryogenesis and is the homolog of a human gene deleted in DiGeorge syndrome.

We report the identification of a mouse gene, Dgcr6, which shows high sequence similarity to gonadal (gdl), a Drosophila gene of unknown function. Dgcr6 is the mouse homolog of human DGCR6, previously shown to be deleted in DiGeorge syndrome, a developmental field defect affecting the derivatives of the pharyngeal arches which is associated with 22q11.2 deletions. The Dgcr6 transcript has a 594 nucleotide open reading frame (ORF) encoding 198 amino acids. We previously mapped Dgcr6 to mouse chromosome 16B1-B3, a region known to contain other mouse homologs of genes deleted in DiGeorge syndrome. Expression studies were performed by Northern blotting analysis on mouse embryo and adult tissues and by RNA in situ hybridization on mouse embryo sections. Results show that Dgcr6 transcripts are abundant during mouse embryogenesis, from at least 7 days post coitum. In particular, high expression was detected in the brain, spinal cord and pharyngeal arches. On adult tissues high expression was detected in testis. The function of Dgcr6 is to be determined, but its developmental expression suggests that this gene may play a role in the developmental defects associated with 22q11.2 deletions.

Amino Acid Sequence↗

PubMed1997

A critical review of research related to family physician-assisted smoking cessation interventions.

A review of family physician-assisted smoking cessation research indicates that the family practice setting affords an excellent opportunity to intervene with a large proportion of smokers, at a time when they are receptive to health promotion messages. Outcome data at 6- and 12-month follow-up intervals indicate the value of combining 3 key strategies in achieving optimal results: physician advice and support, nicotine replacement therapy, and cognitive-behavioural counselling. The authors' review identifies questions that need to be addressed in future research: How can barriers to program delivery be overcome in the family practice setting? What is the best way to ensure optimal integration of the 3 key strategies? Which follow-up intervals are appropriate (e.g., 6 months, 12 months, 18 months) given the finding that relapse is common and that most smokers make several quit attempts before stopping for good?

Follow-Up Studies↗

PubMed1996

A transcription map in the CATCH22 critical region: identification, mapping, and ordering of four novel transcripts expressed in heart.

The acronym CATCH22 is used to indicate collectively a group of related phenotypes, namely velocardiofacial syndrome (VCFS), DiGeorge anomaly (DGA), and conotruncal anomaly face, which are associated with deletions within 22q11.2 in the great majority of patients. A deletion map has allowed us to delimit a smallest region of deletion overlap, considerably smaller than the commonly deleted region. We have mapped within this region the chromosomal breakpoint of a balanced translocation patient presenting with a DGA/VCFS phenotype, making this region the strongest candidate for the location of the gene(s) responsible for the disease phenotype. We report a systematic gene search in this region and show the presence of at least six distinct transcripts, two of which have been previously described. The region searched was approximately 270 kb; therefore, an average of one transcript every 45 kb was found. We generated eight new ESTs and mapped two ESTs present in public databases. All six transcripts are expressed in heart, an organ involved in 70%-80% of CATCH22 patients. We show that the multimethod approach to search for expressed sequences is effective and indeed necessary for a comprehensive search and provides molecular tools for further characterization of the potential genes identified.

Abnormalities, Multiple↗

PubMed1996

Cloning and comparative mapping of a gene from the commonly deleted region of DiGeorge and Velocardiofacial syndromes conserved in C. elegans.

We have identified and cloned a gene, ES2, encoding a putative 476 amino acid protein with a predicted Mr of 52,568. The gene is localized within the DiGeorge/Velocardiofacial syndrome locus on 22q11.2 and is deleted in all the patients in which a deletion within 22q11 could be demonstrated, with the exception of one patient. ES2 is expressed in all the tissues studied. Sequence comparison showed identity with five ESTs and at the amino acid level the sequence was highly similar to, and collinear with, a hypothetical C. elegans protein of unknown function. Mutation analysis was performed in 16 patients without deletion, but no mutation has been found. The cDNA sequence is conserved in mouse and is localized on MMU16B1-B3, known to contain a syntenic group in common with HSA 22q11.2.

Abnormalities, Multiple↗

PubMed1995

LIS2, gene and pseudogene, homologous to LIS1 (lissencephaly 1), located on the short and long arms of chromosome 2.

We report here the isolation of a novel cDNA, designated LIS2, that maps to chromosome 2p11.2 by in situ hybridization and demonstrates extremely high sequence similarity to the recently identified LIS1 gene involved in Miller-Dieker lissencephaly at 17p13.3. Specific probes for LIS2 revealed a pattern of expression resembling that of LIS1, although LIS2 is less abundant. Surprisingly, LIS2 detected an additional, higher molecular weight transcript in adult skeletal muscle. Isolated YAC clones and P1 clones mapped by in situ hybridization to two loci on chromosome 2,2p11.2 and 2q13-q14. This hybridization was due to the existence of LIS2 pseudogene LIS2P on the long arm of chromosome 2.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1995

Smith-Magenis syndrome deletion: a case with equivocal cytogenetic findings resolved by fluorescence in situ hybridization.

The availability of markers for the 17p11.2 region has enabled the diagnosis of Smith-Magenis syndrome (SMS) by fluorescence in situ hybridization (FISH). SMS is typically associated with a discernible deletion of band 17p11.2 upon cytogenetic analysis at a resolution of 400-550 bands. We present a case that illustrates the importance of using FISH to confirm a cytogenetic diagnosis of del(17)(p11.2). Four independent cytogenetic analyses were performed with different conclusions. Results of low resolution analyses of amniocytes and peripheral blood lymphocytes were apparently normal, while high resolution analyses of peripheral blood samples in two laboratories indicated mosaicism for del(17)(p11.2). FISH clearly demonstrated a 17p deletion on one chromosome of all peripheral blood cells analyzed and ruled out mosaicism unambiguously. The deletion was undetectable by flow cytometric quantitation of chromosomal DNA content, suggesting that it is less than 2 Mb. We conclude that FISH should be used to detect the SMS deletion when routine chromosome analysis fails to detect it and to verify mosaicism.

Chromosome Aberrations↗

PubMed1995

Diagnosis of X-linked adrenal hypoplasia congenita by mutation analysis of the DAX1 gene.

OBJECTIVE: To develop a rapid diagnostic approach to individuals with the X-linked cytomegalic form of adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH) due to mutations in DAX1, a new member of the nuclear hormone receptor gene superfamily. DESIGN: Molecular genetic diagnostic investigations of individuals with AHC and their relatives included polymerase chain reaction amplification of DAX1 for identification of intragenic mutations and fluorescence in situ hybridization with a cosmid containing the DAX1 gene for evaluation of larger deletions. PARTICIPANTS: Families that had males affected with AHC were evaluated for mutations involving the DAX1 gene. RESULTS: DAX1 mutations were identified in four families that had males affected with AHC. Two apparently independent pedigrees had an identical frame-shift mutation due to a single base pair deletion, and a third had a larger deletion involving the entire DAX1 locus. The fourth family was evaluated by fluorescence in situ hybridization for prenatal diagnosis, and both the DAX1 locus and the contiguous glycerol kinase region were deleted. CONCLUSIONS: Molecular genetic and molecular cytogenetic techniques represent rapid and complementary approaches to the diagnosis of mutations in the DAX1 gene responsible for AHC and the associated HH. Specific diagnosis of the cause of adrenal insufficiency in these boys permits anticipatory management of the HH and prenatal counseling for parents of the affected child and other members of their families.

Adrenal Insufficiency↗

PubMed1995

Rapid molecular cytogenetic analysis of X-chromosomal microdeletions: fluorescence in situ hybridization (FISH) for complex glycerol kinase deficiency.

Diagnosis of X-chromosomal microdeletions has relied upon the traditional methods of Southern blotting and DNA amplification, with carrier identification requiring time-consuming and unreliable dosage calculations. In this report, we describe rapid molecular cytogenetic identification of deleted DNA in affected males with the Xp21 contiguous gene syndrome (complex glycerol kinase deficiency, CGKD) and female carriers for this disorder. CGKD deletions involve the genes for glycerol kinase, Duchenne muscular dystrophy, and/or adrenal hypoplasia congenita. We report an improved method for diagnosis of deletions in individuals with CGKD and for identification of female carriers within their families, using fluorescence in situ hybridization (FISH) with a cosmid marker (cosmid 35) within the glycerol kinase gene. When used in combination with an Xq control probe, affected males demonstrate a single signal from the control probe, while female carriers demonstrate a normal chromosome with two signals, as well as a deleted chromosome with a single signal from the control probe. FISH analysis for CGKD provides the advantages of speed and accuracy for evaluation of submicroscopic X-chromosomal deletions, particularly in identification of female carriers. In addition to improving carrier evaluation, FISH will make prenatal diagnosis of CGKD more readily available.

Chromosome Mapping↗

PubMed1995

Velo-cardio-facial syndrome: frequency and extent of 22q11 deletions.

Velo-cardio-facial (VCFS) or Shprintzen syndrome is associated with deletions in a region of chromosome 22q11.2 also deleted in DiGeorge anomaly and some forms of congenital heart disease. Due to the variability of phenotype, the evaluation of the incidence of deletions has been hampered by uncertainty of diagnosis. In this study, 54 patients were diagnosed with VCFS by a single group of clinicians using homogeneous clinical criteria independent of the deletion status. Cell lines of these patients were established and the deletion status evaluated for three loci within the commonly deleted region at 22q11.2 using fluorescence in situ hybridization (FISH). In 81% of the patients all three loci were hemizygous. In one patient we observed a smaller interstitial deletion than that defined by the three loci. The phenotype of this patient was not different from that observed in patients with larger deletions.

Abnormalities, Multiple↗

PubMed1995

De novo tandem duplication of chromosome segment 22q11-q12: clinical, cytogenetic, and molecular characterization.

We report on a case of duplication of the segment 22q11-q12 due to a de novo duplication. Molecular cytogenetics studies demonstrated this to be a tandem duplication, flanked proximally by the marker D22Z4, a centromeric alpha satellite DNA repeat, and distally by D22S260, an anonymous DNA marker proximal to the Ewing sarcoma breakpoint. The segment includes the regions responsible for the "cat-eye," Di George, and velo-cardio-facial syndromes and extends distal to the breakpoint cluster region (BCR). The clinical picture is dominated by the cardiac defects and includes findings reminiscent of "cat-eye" syndrome. These findings reinforce the hypothesis that the proximal 22q region contains dosage-sensitive genes involved in development.

Chromosome Aberrations↗

PubMed1995

Submicroscopic deletions at 22q11.2: variability of the clinical picture and delineation of a commonly deleted region.

DiGeorge anomaly (DGA) and velo-cardiofacial syndrome (VCFS) are frequently associated with monosomy of chromosome region 22q11. Most patients have a submicroscopic deletion, recently estimated to be at least 1-2 Mb. It is not clear whether individuals who present with only some of the features of these conditions have the deletion, and if so, whether the size of the deletion varies from those with more classic phenotypes. We have used fluorescence in situ hybridization (FISH) to assess the deletion status of 85 individuals referred to us for molecular analysis, with a wide range of DGA-like or VCFS-like clinical features. The test probe used was the cosmid sc11.1, which detects two loci about 2 Mb apart in 22q11.2. Twenty-four patients carried the deletion. Of the deleted patients, most had classic DGA or VCFS phenotypes, but 6 deleted patients had mild phenotypes, including 2 with minor facial anomalies and velopharyngeal incompetence as the only presenting signs. Despite the great phenotypic variability among the deleted patients, none had a deletion smaller than the 2-Mb region defined by sc11.1. Smaller deletions were not detected in patients with particularly suggestive phenotypes who were not deleted for sc11.1, even when tested with two other probes from the DGA/VCFS region.

Abnormalities, Multiple↗