Potentially effective method for fetal gender determination by noninvasive prenatal testing for X-linked disease.

Examination of maternal plasma cell-free DNA (cfDNA) for noninvasive prenatal testing for fetal trisomy is a highly effective method for pregnant women at high risk. This can be also applied to fetal gender determination in female carriers of severe X-linked disease. Polymerase chain reaction (PCR) analysis is a relatively simpler and less expensive method of detecting Y chromosome-specific repeats (Y-specific PCR; YSP), but is limited by the risk of false-negative results. To address this, we have developed a combined strategy incorporating YSP and an estimation of the fetal DNA fraction. Multiplex PCR for 30 single nucleotide polymorphism (SNP) loci selected by high heterozygosity enables the robust detection of the fetal DNA fraction in cfDNA. The cfDNA sample is first subjected to YSP. When the YSP result is positive, the fetus is male and invasive testing for an X-linked mutation is then required. When the YSP result is negative, the cfDNA sample is analyzed using multiplex PCR. If fetal DNA is then found in the cfDNA, invasive testing is not then required. If the multiplex PCR analysis of cfDNA is negative for fetal DNA, the fetal gender cannot be determined and invasive testing is still required. Our technique provides a potentially effective procedure that can help to avoid unnecessary invasive prenatal testing in some female carriers of severe X-linked disease.

Multiplex PCR in noninvasive prenatal diagnosis for FGFR3-related disorders.

Thanatophoric dysplasia and achondroplasia are allelic disorders caused by a constitutively active mutation in the FGFR3 gene. Because thanatophoric dysplasia is a lethal disorder and achondroplasia is non-lethal, they need to be distinguished after ultrasound identification of fetal growth retardation with short limbs. Accordingly, we have developed a noninvasive prenatal test using cell-free fetal DNA in the maternal circulation to distinguish thanatophoric dysplasia and achondroplasia. A multiplex PCR system encompassing five mutation hotspots in the FGFR3 gene allowed us to efficiently identify the responsible mutation in cell-free DNA in all examined pregnancies with a suspected thanatophoric dysplasia or achondroplasia fetus. This system will be helpful in the differential diagnosis of thanatophoric dysplasia and achondroplasia in early gestation and in couples concerned about the recurrence of thanatophoric dysplasia due to germinal mosaicism.

Increased levels of soluble corin in pre-eclampsia and fetal growth restriction.

Atrial natriuretic peptide is biologically activated by the atrial natriuretic peptide-converting enzyme, corin, and has an important role in regulating blood pressure. We detected elevated serum corin levels in women with pre-eclampsia. Interestingly, the serum corin levels were also found to be elevated in pregnancies with a related disorder, unexplained fetal growth restriction (FGR) without hypertension, suggesting that this phenomenon is not simply a response to maternal hypertension. CORIN mRNA levels were not elevated in placentas from pre-eclampsia or unexplained FGR cases. Likewise, similar signal intensities were found for corin in placental syncytiotrophoblast cells by immunostaining. In contrast, corin signals were higher in maternal decidua cells from pre-eclampsia and unexplained FGR cases. These data suggest that corin may be upregulated in maternal decidua in response to an etiologic pathway that is common to pre-eclampsia and FGR.