Deletions in the Y-derived amelogenin gene fragment in the Indian population.
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BACKGROUND: Rare failures in amelogenin-based gender typing of individuals have been observed globally. In this study, we report the deletion of a large fragment of the amelogenin gene in 10 individuals out of 4,257 male samples analyzed from 104 different endogamous populations of India. METHODS: Samples were analyzed using commercial genetic profiling kits. Those that exhibited failures in amelogenin-based gender identification were further analyzed with published as well as newly designed primers to ascertain the nature and extent of mutation. RESULTS: The failure rate among Indian males was 0.23 %. Though the exact size and nature of the deletion (single point mutations at a number of positions or a single large deletion) could not be determined in the present study, it is inferred that the deletion spans a region downstream of the reverse primer-binding site of commercially available amelogenin primer sets. Deletions were conspicuously absent among the Mongoloid tribes of Northeast India, while both caste and tribal groups harbored these mutations, which was predominantly among the Y-chromosomes belonging to J2 lineage. CONCLUSION: Our study indicates that the different amelogenin primer sets currently included in genetic profiling multiplex kits may result in erroneous interpretations due to mutations undetectable during routine testing. Further there are indications that these mutations could possibly be lineage-specific, inherited deletions. (+info)
Altering biomineralization by protein design.
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To create a bioceramic with unique materials properties, biomineralization exploits cells to create a tissue-specific protein matrix to control the crystal habit, timing, and position of the mineral phase. The biomineralized covering of vertebrate teeth is enamel, a distinctive tissue of ectodermal origin that is collagen-free. In forming enamel, amelogenin is the abundant protein that undergoes self-assembly to contribute to a matrix that guides its own replacement by mineral. Conserved domains in amelogenin suggest their importance to biomineralization. We used gene targeting in mice to replace native amelogenin with one of two engineered amelogenins. Replacement changed enamel organization by altering protein-to-crystallite interactions and crystallite stacking while diminishing the ability of the ameloblast to interact with the matrix. These data demonstrate that ameloblasts must continuously interact with the developing matrix to provide amelogenin-specific protein to protein, protein to mineral, and protein to membrane interactions critical to biomineralization and enamel architecture while suggesting that mutations within conserved amelogenin domains could account for enamel variations preserved in the fossil record. (+info)
Prenatal diagnosis of 46, XX male fetus.
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Prenatal diagnosis of sex differentiation disorders is extremely rare and is estimated in 1/2500 analyzed gestations. A group of this disorders are the 46, XX males and its incidence is estimated in 1/20000 male neonates. We report a male XX fetus in which the diagnosis of sex determination was requested at 20 gestation weeks to clarify the real gender of the fetus. Discrepancy between cytogenetic and ultrasonographic was detected. (+info)
Determination of twin zygosity using a commercially available STR analysis of 15 unlinked loci and the gender-determining marker amelogenin--a preliminary report.
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BACKGROUND: The aim of this preliminary study was to estimate the accuracy of the zygosity determination in twin pregnancies. METHODS: Seventy-three sets of twin pregnancies were enrolled in this study, including 48 sets of twins resulting from assisted reproductive techniques (ART) and 25 sets of spontaneously conceived twins. Determination of zygosity was made by PCR-amplified short tandem repeat (STR) analysis with a commercially available panel, comprising 15 autosomal, codominant, unlinked loci and the gender-determining marker, amelogenin. Monozygotic (MZ) twins were determined when all these unlinked loci and the gender-determining marker were identical. Chorionicity and placenta were examined after delivery of the newborns to check their relationships to the twin zygosities. RESULTS: Three of 48 (6.25%) sets of twins produced by ART and 18 of 25 (72%) sets of spontaneously conceived twins were MZ. Monozygosity could be evaluated based on 'like sex' in spontaneously conceived twins, because they had a greater incidence of MZs than those produced by artificial reproductive techniques. The MZ prediction rate was 78.6%, and the overestimated rate was 21.4% if the monochorionic like-sexed twins (LST) had a grossly single placenta. The underestimated rate of MZs was 26.7% when the dichorionic LST had apparently separate placentas. CONCLUSION: With the DNA-based 15 STR analysis amplified in a multiplex PCR, the determination of the zygosity in multifetal pregnancies is not only cost and time saving but also yields greater sensitivity and precision than conventional methods. (+info)
Diversity of 26-locus Y-STR haplotypes in a Nepalese population sample: isolation and drift in the Himalayas.
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Twenty-six Y-chromosomal short tandem repeat (STR) loci were amplified in a sample of 769 unrelated males from Nepal, using two multiplex polymerase chain reaction (PCR) assays. The 26 loci gave a discriminating power of 0.997, with 59% unique haplotypes, and the highest frequency haplotype occurring 12 times. We identified novel alleles at four loci, microvariants at a further two, and nine examples of amelogenin-Y deletions (1.2%). Comparison with a similarly sized Bhutanese sample typed with the same markers suggested histories of isolation and drift, with drift having a greater effect in Bhutan. Extended (11-locus) haplotypes for the Nepalese samples have been submitted to the Y-STR Haplotype Reference Database (YHRD). (+info)
Amelogenins in human developing and mature dental pulp.
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Amelogenins are a group of heterogenous proteins first identified in developing tooth enamel and reported to be present in odontoblasts. The objective of this study was to elucidate the expression and function of amelogenins in the human dentin-pulp complex. Developing human tooth buds were immunostained for amelogenin, and mRNA was detected by in situ hybridization. The effects of recombinant amelogenins on pulp and papilla cell proliferation were measured by Brd U immunoassay, and differentiation was monitored by alkaline phosphatase expression. Amelogenin protein was found in the forming dentin matrix, and amelogenin mRNA was localized in the dentin, presumably in the odontoblast processes. Proliferation of papilla cells was enhanced by recombinant human amelogenin rH72 (LRAP+ exon 4), while pulp cells responded to both rH72 and rH58 (LRAP), with no effect by rH174. These studies suggest that odontoblasts actively synthesize and secrete amelogenin protein during human tooth development, and that low-molecular-weight amelogenins can enhance pulp cell proliferation. (+info)
The exon 6ABC region of amelogenin mRNA contribute to increased levels of amelogenin mRNA through amelogenin protein-enhanced mRNA stabilization.
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We recently demonstrated that the reuptake of full-length amelogenin protein results in increased levels of amelogenin mRNA through enhanced mRNA stabilization (Xu, L., Harada, H., Tamaki, T. Y., Matsumoto, S., Tanaka, J., and Taniguchi, A. (2006) J. Biol. Chem. 281, 2257-2262). Here, we examined the molecular mechanism of enhanced amelogenin mRNA stabilization. To identify the cis-regulatory region within amelogenin mRNA, we tested various reporter systems using a deletion series of reporter plasmids. A deletion at exon 6ABC of amelogenin mRNA resulted in a 2.5-fold increase in the amelogenin mRNA expression level when compared with that of full-length mRNA, indicating that a cis-element exists in exon 6ABC of amelogenin mRNA. Furthermore, Northwestern analysis demonstrated that amelogenin protein binds directly to its mRNA in vitro, suggesting that amelogenin protein acts as a trans-acting protein that specifically binds to this cis-element. Moreover, recombinant mouse amelogenin protein extended the half-life of full-length amelogenin mRNA but did not significantly alter the half-life of exon 6ABC-deletion mutant mRNA. The splice products produced by deletion of exon 6ABC are known as leucine-rich amelogenin peptides and have signaling effects on cells. Our findings also suggest that the regulation of full-length amelogenin protein expression differs from the regulation of leucine-rich amelogenin peptide expression. (+info)
Origin, splicing, and expression of rodent amelogenin exon 8.
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Amelogenin RNA transcripts undergo extensive alternative splicing, and MMP-20 processes the isoforms following their secretion. Since amelogenins have been ascribed cell-signaling activities, we asked if a lack of proteolytic processing by MMP-20 affects amelogenin signaling and consequently alters amelogenin splice site selection. RT-PCR analyses of amelogenin mRNA between control and Mmp20(-/-)mice revealed no differences in the splicing pattern. We characterized 3 previously unidentified amelogenin alternatively spliced transcripts and demonstrated that exon-8-encoded amelogenin isoforms are processed by MMP-20. Transcripts with exon 8 were expressed approximately five-fold less than those with exon 7. Analyses of the mouse and rat amelogenin gene structures confirmed that exon 8 arose in a duplication of exons 4 through 5, with translocation of the copy downstream of exon 7. No downstream genomic sequences homologous to exons 4-5 were present in the bovine or human amelogenin genes, suggesting that this translocation occurred only in rodents. (+info)