Holoprosencephaly: Characterization of the deletion of 21q22.3 and isolation of cDNAs by a direct selection technique
- Univ. of California, Los Angeles, CA (United States); and others
Holoprosencephaly (HP) is characterized by impaired cleavage of the embryonic forebrain and incomplete mid-facial development. The etiology is heterogeneous and may include aneuploidies for chromosomes 2, 3, 7, 13, 18 and 21. We have narrowed the chromosome 21 candidate region by analyzing 2 cases of HP with deletion 21q22 using FISH and Southern blot techniques. For the smaller deletion, the regions for D21S25, D21S154, D21S171 and D21S44 were deleted and for D21S42 was not. Combining these data with previous reports of deletion of 21q22.3 (ColVIA2-ter) without the holoprosencephaly phenotype indicate that the region responsible for holoprosencephaly spans the 2-3 Mb region including PFKL and ITGB2 (CD18) that has also been linked to progressive myoclonus epilepsy (EPM1). In order to isolate genes responsible for these diseases, we constructed a cDNA library from a 14-week trisomy 21 fetal brain using Uni-Zap XR (Stratagene). More than 95% clones have inserts ranging from 1-4 kb (ave. 2 kb). In addition we applied a direct cDNA selection method to BACs (Bacterial Artificial Chromosomes) in the 21q22.3 region. Using cDNA synthesized from trisomy 21 fetal brain, we attached Sau3AI linkers, digested with Sau3AI, attached second linkers and hybridized to biotinylated BAC DNAs which cover the candidate region. cDNA/BAC DNA hybrid molecules were captured on streptavidin-coated magnetic beads, non-specific cDNA were washed out, and specifically hybridized cDNA were eluted and amplified by PCR. Twice-selected PCR products were subcloned and analyzed. Southern blot analyses revealed that 21 out of 30 (70%) of fragments yielded unique bands on the original BACs. Eight clones contained repetitive sequences. We are now isolating cDNAs expressed in the Down syndrome fetal brain using these cDNA fragments. These genes now provide candidates for EPM1 and holoprosencephaly.
- OSTI ID:
- 134498
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-1232
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BASIC STUDIES
HUMAN CHROMOSOME 21
GENETIC MAPPING
DNA-CLONING
DNA SEQUENCING
CHROMOSOMAL ABERRATIONS
GENES
CONGENITAL MALFORMATIONS
ETIOLOGY
PATIENTS
HEREDITARY DISEASES
PHENOTYPE
HUMAN CHROMOSOMES
ANEUPLOIDY
DNA HYBRIDIZATION
FLUORESCENCE
BIOLOGICAL MARKERS
POLYMERASE CHAIN REACTION
BACTERIA