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Technical Briefs |
Departments of
1
Chemical Pathology and
2
Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong SAR
3 Department of Paediatrics, The University of Hong Kong, Hong Kong SAR
aaddress correspondence to this author at: Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Room 38023, 1/F Clinical Sciences Building, 30-32 Ngan Shing St., Shatin, New Territories, Hong Kong SAR; fax 852-2194-6171, e-mail loym@cuhk.edu.hk
The presence of fetal DNA in maternal plasma has allowed the development of strategies for noninvasive prenatal diagnosis (1). However, because fetal DNA in maternal plasma circulates among a background of maternal DNA, strategies for noninvasive prenatal diagnosis with applications of fetal DNA in maternal plasma have been confined to the detection of autosomal dominant, paternally inherited genetic traits, such as fetal gender (for sex-linked disorders) (1), rhesus D (2)(3), myotonic dystrophy (4), and achondroplasia (5). Using congenital adrenal hyperplasia (CAH) as a model system, we present a strategy for the noninvasive prenatal exclusion of an autosomal recessive condition through the detection of fetal DNA in maternal plasma. The approach described in this study may potentially be applicable to other autosomal recessive conditions.
More than 90% of cases of CAH are a result of deficiency of 21-hydroxylase, an enzyme of the adrenal gland involved in the synthesis of glucocorticoids and mineralocorticoids. 21-Hydroxylase is encoded by CYP21, a MHC class III gene located on chromosome 6p21.3. Most mutations causing 21-hydroxylase deficiency are caused by either gene deletions or gene conversions, whereby deleterious mutations are transferred from the nearby pseudogene, CYP21P, which shares 98% homology with CYP21 (6). Consequent to profound deficiency or the complete absence of activity of 21-hydroxylase, severe forms of CAH manifest as salt-wasting attributable to impaired synthesis of mineralocorticoids and glucocorticoids. In addition, the excess buildup of metabolic precursors causes excessive androgen production, leading to virilization of female fetuses (6). Hence, dexamethasone therapy is customarily prescribed prenatally to prevent in utero virilization of an affected female
Acknowledgments
References
The following articles in journals at HighWire Press have cited this article:
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  Y.M DENNIS LO Fetal DNA in Maternal Plasma: Progress through Epigenetics. Ann. N.Y. Acad. Sci., September 1, 2006; 1075: 74 - 80. [Abstract] [Full Text] [PDF]
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 K.C. A. Chan, A. B.Y. Hui, N. Wong, T. K. Lau, T. N. Leung, K.-W. Lo, and Y.M. D. Lo Investigation of the Genomic Representation of Plasma DNA in Pregnant Women by Comparative Genomic Hybridization Analysis: A Feasibility Study Clin. Chem., December 1, 2005; 51(12): 2398 - 2401. [Full Text] [PDF]
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 Y.M. D. Lo Recent Advances in Fetal Nucleic Acids in Maternal Plasma J. Histochem. Cytochem., March 1, 2005; 53(3): 293 - 296. [Abstract] [Full Text] [PDF]
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 F. Z. Bischoff, D. E. Lewis, and J. L. Simpson Cell-free fetal DNA in maternal blood: kinetics, source and structure Hum. Reprod. Update, January 1, 2005; 11(1): 59 - 67. [Abstract] [Full Text] [PDF]
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 C. Ding, R. W. K. Chiu, T. K. Lau, T. N. Leung, L. C. Chan, A. Y. Y. Chan, P. Charoenkwan, I. S. L. Ng, H.-y. Law, E. S. K. Ma, et al. MS analysis of single-nucleotide differences in circulating nucleic acids: Application to noninvasive prenatal diagnosis PNAS, July 20, 2004; 101(29): 10762 - 10767. [Abstract] [Full Text] [PDF]
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T. WATAGANARA and D. W. BIANCHI Fetal Cell-Free Nucleic Acids in the Maternal Circulation: New Clinical Applications Ann. N.Y. Acad. Sci., June 1, 2004; 1022(1): 90 - 99. [Abstract] [Full Text] [PDF]
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Y. Li, B. Zimmermann, C. Rusterholz, A. Kang, W. Holzgreve, and S. Hahn Size Separation of Circulatory DNA in Maternal Plasma Permits Ready Detection of Fetal DNA Polymorphisms Clin. Chem., June 1, 2004; 50(6): 1002 - 1011. [Abstract] [Full Text] [PDF]
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 H Masuzaki, K Miura, K-i Yoshiura, S Yoshimura, N Niikawa, and T Ishimaru Detection of cell free placental DNA in maternal plasma: direct evidence from three cases of confined placental mosaicism J. Med. Genet., April 1, 2004; 41(4): 289 - 292. [Full Text] [PDF]
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K.C. A. Chan, J. Zhang, A. B.Y. Hui, N. Wong, T. K. Lau, T. N. Leung, K.-W. Lo, D. W.S. Huang, and Y.M. D. Lo Size Distributions of Maternal and Fetal DNA in Maternal Plasma Clin. Chem., January 1, 2004; 50(1): 88 - 92. [Abstract] [Full Text] [PDF]
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 J. Guibert, A. Benachi, A.-G. Grebille, P. Ernault, J.-R. Zorn, and J.-M. Costa Kinetics of SRY gene appearance in maternal serum: detection by real time PCR in early pregnancy after assisted reproductive technique Hum. Reprod., August 1, 2003; 18(8): 1733 - 1736. [Abstract] [Full Text] [PDF]
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D. W. Bianchi Prenatal Exclusion of Recessively Inherited Disorders: Should Maternal Plasma Analysis Precede Invasive Techniques? Clin. Chem., May 1, 2002; 48(5): 689 - 690. [Full Text] [PDF]
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