Biallelic mutations in LEPRE1 result in recessively inherited forms of osteogenesis imperfecta (OI) that are often lethal in the perinatal period. A mutation (c.1080+1G>T, IVS5+1G>T) in African Americans has a carrier frequency of about 1/240. The mutant allele originated in West Africa in tribes of Ghana and Nigeria where the carrier frequencies are 2% and 5%. By examining 200 samples from an African-derived population in Tobago and reviewing hospital neonatal death records, we determined that the carrier frequency of c.1080+1G>T was about one in 200 and did not contribute to the neonatal deaths recorded over a 3-year period of time in Trinidad. In the course of sequence analysis, we found surprisingly high LEPRE1 allelic diversity in the Tobago DNA samples in which there were 11 alleles distinguished by a single basepair variant in or near exon 5. All the alleles found in the Tobago population that were within the sequence analysis region were found in the African American population in the Exome Variant Project. This diversity appeared to reflect the geographic origin of the original population in Tobago. In 44 individuals with biallelic LEPRE1 mutations identified by clinical diagnostic testing, we found the sequence alterations occurred on seven of the 11 variant alleles. All but one of the mutations identified resulted in mRNA or protein instability for the majority of the transcripts from the altered allele. These findings suggest that the milder end of the clinical spectrum could be due to as yet unidentified missense mutations in LEPRE1.
Keywords: African; LEPRE1; allelic diversity; allelic heterogeneity; mutations; neonatal death; osteogenesis imperfecta.