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L G Biesecker

Publications and source records attributed to L G Biesecker.

At least 55 records · Page 3Linked to original sources
PubMed1997

Gene structure and allelic expression assay of the human GLI3 gene.

The GLI3 gene encodes a putative zinc finger transcription factor that is important in early vertebrate development. Haploinsufficiency of this gene has been associated with the Greig cephalopolysyndactyly syndrome and truncation mutations cause Pallister-Hall syndrome. In the course of studies to determine the etiology of Pallister-Hall syndrome, we required knowledge of the fine structure of GLI3 to perform detailed genetic and physical mapping and mutation screening of this gene. The coding region of GLI3 is composed of 14 exons, including a large exon of more than 2500 bp. In addition, the gene contains two intragenic dinucleotide repeats, and four single-base pair polymorphisms in the coding region. We have used these coding region polymorphisms to design an allele-specific expression study that will be useful for studying patients with Greig cephalopolysyndactyly syndrome. In addition, GLI3 should be considered a candidate gene for related developmental anomalies of humans. Such hypotheses will be more readily addressed with the availability of the fine structure of the gene and the allele-expression assay.

Abnormalities, Multiple↗
PubMed1997

GLI3 frameshift mutations cause autosomal dominant Pallister-Hall syndrome.

Pallister-Hall syndrome (PHS, M146510) was first described in 1980 in six newborns. It is a pleiotropic disorder of human development that comprises hypothalamic hamartoma, central polydactyly, and other malformations. This disorder is inherited as an autosomal dominant trait and has been mapped to 7p13 (S. Kang et al. Autosomal dominant Pallister-Hall syndrome maps to 7p13. Am. J. Hum. Genet. 59, A81 (1996)), co-localizing the PHS locus and the GLI3 zinc finger transcription factor gene. Large deletions or translocations resulting in haploinsufficiency of the GLI3 gene have been associated with Greig cephalopolysyndactyly syndrome (GCPS; M175700) although no mutations have been identified in GCPS patients with normal karyotypes. Both PHS and GCPS have polysyndactyly, abnormal craniofacial features and are inherited in an autosomal dominant pattern, but they are clinically distinct. The polydactyly of GCPS is commonly preaxial and that of PHS is typically central or postaxial. No reported cases of GCPS have hypothalamic hamartoma and PHS does not cause hypertelorism or broadening of the nasal root or forehead. The co-localization of the loci for PHS and GCPS led us to investigate GLI3 as a candidate gene for PHS. Herein we report two PHS families with frameshift mutations in GLI3 that are 3' of the zinc finger-encoding domains, including one family with a de novo mutation. These data implicate mutations in GLI3 as the cause of autosomal dominant PHS, and suggest that frameshift mutations of the GLI3 transcription factor gene can alter the development of multiple organ systems in vertebrates.

Abnormalities, Multiple↗
PubMed1997

Characterization of short tandem repeats from thirty-one human telomeres.

Completion of genetic and physical maps requires markers from the ends (telomeres) of every human chromosome. We have searched for short tandem repeats (microsatellites) in cosmid and P1 clones and generated 661 sequence-tagged sites (STS) from the terminal 300 kb of 31 human chromosome ends. PCR assays were successfully designed for 58 microsatellites and mapped both genetically and on radiation hybrids (RHs) to confirm their telomeric location. Sequence analysis revealed marked variation in sequence composition, consistent with the hypothesis that even very highly GC-rich chromosome bands (the T bands) are not homogenous. The STSs that we have generated will be a necessary resource for the construction of physical maps of these complex regions of the genome.

Base Sequence↗
PubMed1997

Linkage mapping and phenotypic analysis of autosomal dominant Pallister-Hall syndrome.

Pallister-Hall syndrome is a human developmental disorder that is inherited in an autosomal dominant pattern. The phenotypic features of the syndrome include hypothalamic hamartoma, polydactyly, imperforate anus, laryngeal clefting, and other anomalies. Here we describe the clinical characterisation of a family with 22 affected members and the genetic mapping of the corresponding locus. Clinical, radiographic, and endoscopic evaluations showed that this disorder is a fully penetrant trait with variable expressivity and low morbidity. By analysing 60 subjects in two families using anonymous STRP markers, we have established linkage to 7p13 by two point analysis with D7S691 resulting in a lod score of 7.0 at theta = 0, near the GLI3 locus. Deletions and translocations in GLI3 are associated with the Greig cephalopolysyndactyly syndrome. Although Greig cephalopolysyndactyly syndrome has some phenotypic overlap with Pallister-Hall syndrome, these two disorders are clinically distinct. The colocalisation of loci for these distinct phenotypes led us to analyse GLI3 for mutations in patients with Pallister-Hall syndrome. We have previously shown GLI3 mutations in two other small, moderately affected families with Pallister-Hall syndrome. The linkage data reported here suggest that these larger, mildly affected families may also have mutations in GLI3.

Abnormalities, Multiple↗
PubMed1996

Isolation of the human chromosome 22q telomere and its application to detection of cryptic chromosomal abnormalities.

A number of human telomeres have been successfully cloned using a modified yeast artificial chromosome (YAC) vector (half-YAC) cloning strategy, but to date, human chromosome 22q has not been identified by this approach. We used an alternative approach of genomic walking, starting from a subtelomeric sequence, Tel-Bam3.4. present on a number of human chromosomes including 22q. This approach was successful in the development of a cosmid contig representing the terminal 140 kb of human chromosome 22q, providing telomeric closure of the genetic and physical maps for 22q. The most distal region of the contig contains subtelomeric repeats which crosshybridize to a number of chromosomes, while the proximal sequences are unique for 22q. The unique sequence cosmid was used as a 22qter-specific probe for fluorescence in situ hybridization (FISH) analysis, which confirmed that this cosmid was distal to the most telomeric marker previously available for chromosome 22. In addition, this cosmid was used to document a 22q terminal deletion that was not detectable by conventional cytogenetic analysis. Unique telomere-specific FISH probes such as this one will have significant diagnostic value in the detection of cryptic deletions and translocations in patients with unexplained mental retardation and other patient populations.

Cerebroside-Sulfatase↗
PubMed1996

Orphan tests.

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Ethics Committees, Research↗
PubMed1996

Exclusion of candidate loci and cholesterol biosynthetic abnormalities in familial Pallister-Hall syndrome.

Pallister-Hall syndrome (PHS) was originally described in 1980 in six sporadic cases of children with structural anomalies including hypothalamic hamartoma, polydactyly, imperforate anus, and renal and pulmonary anomalies. In 1993, the first familial cases were reported, including affected sibs and vertical transmission. Three of these families are sufficiently large to allow initial evaluation by linkage studies to candidate genes or loci. We have evaluated candidate loci for PHS based on three clinical observations. The first is a patient with PHS-like malformations, including a hypothalamic hamartoma, and an unbalanced translocation involving 7q and 3p. The second is a family with familial PHS where the founder's father had an autosomal dominant hand malformation previously mapped to 17q. The third is the phenotypic overlap of PHS and Smith-Lemli-Opitz syndrome. In this report, we exclude these loci as candidates for linkage to the PHS phenotype on the basis of lod scores of less than-2.0. We conclude that hypothalamic hamartoma is not specific to PHS and that the dominant hand malformation in one of the families was a coincidence. To evaluate the relationship of PHS to Smith-Lemli-Opitz syndrome, we analysed levels of cholesterol and intermediate metabolites of the later stages of cholesterol biosynthesis. There is no evidence of a generalised disorder of cholesterol biosynthesis in patients with familial PHS. On genetic and biochemical grounds, we conclude that PHS and Smith-Lemli-Opitz syndrome are not allelic variants of a single locus.

Cholesterol↗
PubMed1995

Detection of a subtle rearrangement of chromosome 22 using molecular techniques.

Conventional cytogenetics is a useful clinical tool that has a lower limit of sensitivity of 2-5 Mb for detection of duplications or deletions. Because the threshold of clinically significant aneusomy is below this range, there is a need for approaches to improve the sensitivity of the detection of aneusomy. We have implemented a system of screening for subtle unbalanced translocations in children with multiple congenital anomalies of unknown cause. Our approach uses subtelomeric microsatellite markers to detect small areas of segmental aneusomy due to unbalanced translocations. Herein we report a patient with severe multiple congenital anomalies and a normal karyotype who was diagnosed by this approach. Microsatellite markers from 41 telomeres were analyzed and were normal with the exception of those on distal chromosome 22. Further analysis with additional microsatellites and fluorescent in situ hybridization confirmed duplication of 22q13.2-qter. We conclude that microsatellite screening can detect subtle unbalanced translocations in children with severe anomalies.

Abnormalities, Multiple↗
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

Identification of alternative exons, including a novel exon, in the tyrosine kinase receptor gene Etk2/tyro3 that explain differences in 5' cDNA sequences.

Protein tyrosine kinase transmembrane receptors trigger signal transduction cascades upon ligand binding, resulting in cellular proliferation, differentiation, differentiation inhibition or apoptosis depending upon the cell target. The ETK2/TYRO3 receptor is a tyrosine kinase expressed in embryonic stem cells, brain and testis that has recently been cloned by several groups. Analysis of cDNA clones isolated from several tissues shows 2 isoforms of the Etk2/tyro3 gene product that result from usage of alternative exons near the 5' end of the gene. In addition, our data suggest that a third alternative exon is positioned between these two alternative exons. This novel exon encodes yet another isoform that predicts a unique amino-terminal protein sequence. The alternative exons (exons 2A, 2B and 2C), predict three isoforms with different initiation codons, signal sequences and lengths. The existence of these multiple isoforms may be important for protein processing, translocation, or function.

Alternative Splicing↗