Profound biotinidase deficiency caused by a point mutation that creates a downstream cryptic 3' splice acceptor site within an exon of the human biotinidase gene. 1997

R J Pomponio, and T R Reynolds, and H Mandel, and O Admoni, and P D Melone, and G A Buck, and B Wolf
Department of Human Genetics, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.

Biotinidase recycles the vitamin biotin from biocytin upon the degradation of the biotin-dependent carboxylases. We have identified a novel point mutation within the biotinidase gene that encodes the signal peptide in two unrelated individuals with profound biotinidase deficiency. Sequence analysis of genomic DNA from these individuals revealed a G to A transition (G100-->A) located 57 bases downstream of the authentic splice acceptor site in exon B. Although this mutation predicts a G34S substitution, it also generates a 3' splice acceptor site. Sequence of the PCR-amplified cDNA from the homozygous child revealed that all the product was shorter than that of normal individuals and was the result of aberrant splicing. The aberrantly spliced transcript lacked 57 bases, including a second in-frame ATG, that encode most of the putative signal peptide and results in an in-frame deletion of 19 amino acids. The mutation results in failure to secrete the aberrant protein into the blood. This is the first reported example in which a point mutation creates a cryptic 3' splice acceptor site motif that is used preferentially over the upstream authentic splice site. The preferential usage of the downstream splice site is not consistent with the 5'-3' scanning model, but is consistent with the exon definition model of RNA splicing.

UI MeSH Term Description Entries
D007231 Infant, Newborn An infant during the first 28 days after birth. Neonate,Newborns,Infants, Newborn,Neonates,Newborn,Newborn Infant,Newborn Infants
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008214 Lymphocytes White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS. Lymphoid Cells,Cell, Lymphoid,Cells, Lymphoid,Lymphocyte,Lymphoid Cell
D008297 Male Males
D009100 Multiple Carboxylase Deficiency A deficiency in the activities of biotin-dependent enzymes (propionyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, and PYRUVATE CARBOXYLASE) due to one of two defects in BIOTIN metabolism. The neonatal form is due to HOLOCARBOXYLASE SYNTHETASE DEFICIENCY. The late-onset form is due to BIOTINIDASE DEFICIENCY. Carboxylase Deficiency, Multiple,Combined Carboxylase Deficiency,Carboxylase Deficiency, Combined,Deficiency, Combined Carboxylase,Deficiency, Multiple Carboxylase,Carboxylase Deficiencies, Combined,Carboxylase Deficiencies, Multiple,Combined Carboxylase Deficiencies,Deficiencies, Combined Carboxylase,Deficiencies, Multiple Carboxylase,Multiple Carboxylase Deficiencies
D010375 Pedigree The record of descent or ancestry, particularly of a particular condition or trait, indicating individual family members, their relationships, and their status with respect to the trait or condition. Family Tree,Genealogical Tree,Genealogic Tree,Genetic Identity,Identity, Genetic,Family Trees,Genealogic Trees,Genealogical Trees,Genetic Identities,Identities, Genetic,Tree, Family,Tree, Genealogic,Tree, Genealogical,Trees, Family,Trees, Genealogic,Trees, Genealogical
D011247 Pregnancy The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH. Gestation,Pregnancies
D002675 Child, Preschool A child between the ages of 2 and 5. Children, Preschool,Preschool Child,Preschool Children
D005091 Exons The parts of a transcript of a split GENE remaining after the INTRONS are removed. They are spliced together to become a MESSENGER RNA or other functional RNA. Mini-Exon,Exon,Mini Exon,Mini-Exons
D005260 Female Females

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