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Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome
BACKGROUND: Trisomy 21 Down syndrome is the most common genetic cause for congenital malformations and intellectual disability. It is well known that in the outstanding majority of cases the extra chromosome 21 originates from the mother but only in less than 10 % from the father. The mechanism unde...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4545544/ https://www.ncbi.nlm.nih.gov/pubmed/26300975 http://dx.doi.org/10.1186/s13039-015-0155-2 |
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author | Iwarsson, Erik Kvist, Ulrik Hultén, Maj A. |
author_facet | Iwarsson, Erik Kvist, Ulrik Hultén, Maj A. |
author_sort | Iwarsson, Erik |
collection | PubMed |
description | BACKGROUND: Trisomy 21 Down syndrome is the most common genetic cause for congenital malformations and intellectual disability. It is well known that in the outstanding majority of cases the extra chromosome 21 originates from the mother but only in less than 10 % from the father. The mechanism underlying this striking difference in parental origin of Trisomy 21 Down syndrome is still unknown. However, it seems likely that the main reason is a much higher stringency in the elimination of any trisomy 21 cells during fetal testicular than ovarian development. We have here focussed attention on the paternal gametic output, i.e. the incidence of disomy 21 in spermatozoa. RESULTS: We have used fluorescence in situ hybridisation (FISH) to determine the copy number of chromosome 21 in spermatozoa from 11 men with normal spermiograms. Due to the well-known risk of false positive and false negative signals using a single FISH probe, we have applied two chromosome 21q probes, and we have added a chromosome 18-specific probe to allow differentiation between disomy 21 and diploidy. Analysing a total number of 2000 spermatozoa per case, we documented an average incidence of disomy 21 at 0.13 %, with a range of 0.00-0.25 % and a SD of 0.08. There was no indication of diploidy in this cohort of 22,000 sperm. CONCLUSION: Numerous previous studies on the incidence of disomy 21 in sperm have been published, using FISH. As far as we are aware, none of these have applied more than a single chromosome 21-specific probe. Accepting our mean of 0.13 % of disomy 21, and providing there is no selective fertilisation capability of disomy 21 sperm in relation to the normal, we conclude that around 1 in 800 conceptions is expected to be trisomic for chromosome 21 of paternal origin. Bearing in mind that the maternal origin likely is at least 10 times more common, we tentatively propose that around 1 in 80 oocytes in the maternal ovarian reserve may be disomy 21. One reason for this discrepancy may be a more stringent selection against aberrant chromosome numbers during spermatogenesis than oogenesis. Further work is required to determine the relevant stages of spermatogenesis at which such a selection may take place. |
format | Online Article Text |
id | pubmed-4545544 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-45455442015-08-23 Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome Iwarsson, Erik Kvist, Ulrik Hultén, Maj A. Mol Cytogenet Research BACKGROUND: Trisomy 21 Down syndrome is the most common genetic cause for congenital malformations and intellectual disability. It is well known that in the outstanding majority of cases the extra chromosome 21 originates from the mother but only in less than 10 % from the father. The mechanism underlying this striking difference in parental origin of Trisomy 21 Down syndrome is still unknown. However, it seems likely that the main reason is a much higher stringency in the elimination of any trisomy 21 cells during fetal testicular than ovarian development. We have here focussed attention on the paternal gametic output, i.e. the incidence of disomy 21 in spermatozoa. RESULTS: We have used fluorescence in situ hybridisation (FISH) to determine the copy number of chromosome 21 in spermatozoa from 11 men with normal spermiograms. Due to the well-known risk of false positive and false negative signals using a single FISH probe, we have applied two chromosome 21q probes, and we have added a chromosome 18-specific probe to allow differentiation between disomy 21 and diploidy. Analysing a total number of 2000 spermatozoa per case, we documented an average incidence of disomy 21 at 0.13 %, with a range of 0.00-0.25 % and a SD of 0.08. There was no indication of diploidy in this cohort of 22,000 sperm. CONCLUSION: Numerous previous studies on the incidence of disomy 21 in sperm have been published, using FISH. As far as we are aware, none of these have applied more than a single chromosome 21-specific probe. Accepting our mean of 0.13 % of disomy 21, and providing there is no selective fertilisation capability of disomy 21 sperm in relation to the normal, we conclude that around 1 in 800 conceptions is expected to be trisomic for chromosome 21 of paternal origin. Bearing in mind that the maternal origin likely is at least 10 times more common, we tentatively propose that around 1 in 80 oocytes in the maternal ovarian reserve may be disomy 21. One reason for this discrepancy may be a more stringent selection against aberrant chromosome numbers during spermatogenesis than oogenesis. Further work is required to determine the relevant stages of spermatogenesis at which such a selection may take place. BioMed Central 2015-08-19 /pmc/articles/PMC4545544/ /pubmed/26300975 http://dx.doi.org/10.1186/s13039-015-0155-2 Text en © Iwarsson et al. 2015 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
spellingShingle | Research Iwarsson, Erik Kvist, Ulrik Hultén, Maj A. Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome |
title | Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome |
title_full | Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome |
title_fullStr | Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome |
title_full_unstemmed | Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome |
title_short | Disomy 21 in spermatozoa and the paternal origin of trisomy 21 Down syndrome |
title_sort | disomy 21 in spermatozoa and the paternal origin of trisomy 21 down syndrome |
topic | Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4545544/ https://www.ncbi.nlm.nih.gov/pubmed/26300975 http://dx.doi.org/10.1186/s13039-015-0155-2 |
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