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The genetically programmed down-regulation of lactase in children
Y Wang1, C B Harvey, E J Hollox
1Medical Research Council Human Biochemical Genetics Unit, University College London, England.
Gastroenterology
|June 3, 1998
Summary
The genetic basis for lactase persistence or nonpersistence in children begins before age five. This lactase gene down-regulation is detectable from the second year of life, though its timing varies.
Area of Science:
- Genetics
- Molecular Biology
- Pediatrics
Background:
- Lactase activity is high in infants but varies in adults due to a genetic polymorphism affecting lactase gene mRNA expression.
- This polymorphism determines lactase persistence (high activity) or nonpersistence (low activity).
Purpose of the Study:
- To investigate the age of onset for the lactase persistence/nonpersistence genetic polymorphism expression in children.
Main Methods:
- Analysis of lactase activity in 866 children's biopsy specimens across different ages.
- Semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) on RNA from 32 pediatric samples (aged 2-132 months).
- Use of marker polymorphisms to determine the allelic origin of lactase mRNA transcripts.
Main Results:
- Evidence suggests the lactase persistence/nonpersistence polymorphism emerges before five years of age.
- In children aged 2-132 months, lactase mRNA and activity were generally high.
- Allelic expression showed increasing asymmetry with age, with one allele becoming undetectable by 11 years old, similar to adult patterns.
Conclusions:
- Genetically programmed down-regulation of the lactase gene is detectable in children starting from their second year of life.
- The onset and degree of this down-regulation exhibit some variability among individuals.
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