الفهرس 
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Abstract
Prenatal DNA diagnosis of Achondroplasia from Maternal Plasma
Achondroplasia is the most common form of human dwarfism and the mutation causing it might be the most common disease-causing mutation to arise de novo in human beings.
Mutations of the gene for fibroblast growth factor receptor 3 (FGFR3), were discovered in achondroplasia over a decade ago.
The FGFR3 gene maps to human chromosome 4p16.3 and provides instructions for making a protein called fibroblast growth factor receptor 3. Developmental expression of FGFR3 suggests this protein plays a significant role in skeletal development.
Prenatal DNA diagnosis is usually done via invasive procedures such as amniocentesis and chorionic villous sampling. Fetal nucleated erythrocytes in maternal blood have been proposed as potential target cells for non-invasive prenatal diagnosis. However, the presence of fetal nucleated erythrocytes in maternal blood is extremely rare. Since 1997, detection of cell-free fetal DNA in maternal plasma and serum has been done by assessment of Y-chromosomal sequences in pregnant women bearing male fetuses or the rhesus-factor gene in rhesus-negative pregnant women. Therefore, maternal plasma may have the potential to provide for non-invasive prenatal diagnosis of single-gene disorders in which the mother does not have genomic alterations in the target sequence.
The aim of the present work was to attempting prenatal DNA diagnosis of achondroplasia from the maternal plasma. This study was carried out on 97 selected cases of non achondroplsic pregnancies whose their fetuses clinically suspected to have achondroplasia by Ultrasonography in a period of 7 years and 50 unaffected pregnancies served as controls. All studied subjects were submitted to Ultrasonography investigation between 27-40 weeks of gestation, no other abnormality was detected by magnetic resonance imaging. Genotyping of the studied subjects for two common mutations of the FGFR3 gene was performed by PCR-RFLP analysis.
Our results indicate that all affected fetuses suspected to have achondroplsic manifestations by Ultrasonography, their fetal DNA was extracted from their maternal plasma. Two common mutations, G380A and G380C, at protein position 380 in the transmembrane domain of the fibroblast receptor 3 gene were determined in a ratio of 97% 3 % respectively have achondroplasia . It can be concluded that we succeeded to attempt prenatal DNA diagnosis of achondroplasia from maternal plasma between 27 and 40 weeks of gestation and confirmed previous studies that more than 90% of the patients with achondroplasia from different ethnic groups carry the G380R mutation resulting from G to A transition at position 1138 in FGFR3 gene.