Prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism detected by array comparative genomic hybridization

Prenatal diagnosis of familial 3p26.3p25.3 deletion in a pregnancy associated with a favorable fetal outcome and asymptomatic carrier parent and family members in three generations

OBJECTIVE

We present prenatal diagnosis of familial 3p26.3p25.3 deletion in a pregnancy associated with a favorable fetal outcome and asymptomatic carrier parent and family members in three generations.

CASE REPORT

A 35-year-old, gravida 2, para 1, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age and the carrier of distal 3p deletion. She was phenotypically normal, and there was no family history of congenital anomalies. Amniocentesis revealed a karyotype of 46,XY,del(3)(p26.1). Repeat amniocentesis at 21 weeks of gestation revealed a karyotype of 46,XY,del(3)(p25.3). Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes showed the result of arr 3p26.3p25.3 (117,735-8,709,972) × 1.0 [GRCh37 (hg19)] with an 8.59-Mb deletion of 3p26.3p25.3 encompassing 14 OMIM genes of CHL1, CNTN6, CNTN4, IL5RA, TRNT1, CRBN, SETMAR, SUMF1, ITPR1, BHLHE40, ARL8B, GRM7, LMCD1 and SSUH2. Cytogenetic analysis of parental bloods revealed a karyotype of 46,XX,del (3) (p25.3) in the mother and 46,XY in the father. The woman's 69-year-old mother and her 2-year-old elder son carried the same aberrant chromosome of 3p25.3→p26.3 deletion by conventional cytogenetic analysis but manifested no phenotypic abnormality. aCGH analysis of the peripheral bloods showed that the woman's mother and her elder son had the same 8.59-Mb deletion of 3p26.3p25.3. The woman was advised to continue the pregnancy. At 39 weeks of gestation, a 3040-g healthy male baby was delivered. When follow-up at age 2½ years, the neonate was normal in development and showed no apparent phenotypic abnormality.

CONCLUSION

Distal 3p deletion of 3p26.3p25.3 involving the OMIM genes from CHL1 to SSUH2 can be associated with no apparent phenotypic abnormality.

Fetal Cystic Hygroma Associated with Terminal 2p25.1 Duplication and Terminal 3p25.3 Deletion: Cytogenetic, Fluorescent in Situ Hybridization and Microarray Familial Characterization of Two Different Chromosomal Structural Rearrangements

We report a prenatally diagnosed case of partial trisomy 2p and partial monosomy 3p, resulting from unbalanced translocation (2;3)(p25.1;p25.3) of paternal origin. Parents were non consanguineous Caucasians, with familial history of recurrent miscarriages on the father’s side. Detailed sonographic examination of the fetus showed a septated cystic hygroma measuring 6 mm at 13 weeks’ gestation. Karyotyping and fluorescent in situ hybridization (FISH) analysis of cultured amniotic fluid cells revealed an unbalanced translocation der(3)t(2;3)(p25.1; p25.3) and apparently balanced inv(3)(p13p25.3) in a fetus. Parental cytogenetic evaluation using karyotyping and FISH analysis showed the presence of both a balanced translocation and a paracentric inversion in father t(2;3) (p25.1;p25.3) inv(3)(p13p25.3). Microarray analysis showed a 11.6 Mb deletion at 3p26.3-p25.3 and duplication of 10.5 Mb at the 2p25.3-p25 region. The duplicated region at 2p25.1p25.3 contains 45 different genes, where 12 are reported as OMIM morbid genes with different phenotypical implications. The deleted region at 3p26.3-p25.3 contains 65 genes, out of which 27 are OMIM genes.

Three of these (CNTN4, SETD5 and VHL) were curated by Clingene Dosage Gene Map and were given a high haplo-insufficiency score. Genes affected by the unbalanced translocation could have contributed to some specific phenotypic changes of the fetus in late pregnancy. The application of different cytogenetic methods was essential in our case, allowing the detection of different types of structural chromosomal aberrations and more thorough genetic counseling for future pregnancies.

Neuronal migration genes and a familial translocation t (3;17): candidate genes implicated in the phenotype

BACKGROUND

While Miller-Dieker syndrome critical region deletions are well known delineated anomalies, submicroscopic duplications in this region have recently emerged as a new distinctive syndrome. So far, only few cases have been described overlapping 17p13.3 duplications.

METHODS

In this study, we report on clinical and cytogenetic characterization of two new cases involving 17p13.3 and 3p26 chromosomal regions in two sisters with familial history of lissencephaly. Fluorescent In Situ Hybridization and array Comparative Genomic Hybridization were performed.

RESULTS

A deletion including the critical region of the Miller-Dieker syndrome of at least 2,9 Mb and a duplication of at least 3,6 Mb on the short arm of chromosome 3 were highlighted in one case. The opposite rearrangements, 17p13.3 duplication and 3p deletion, were observed in the second case. This double chromosomal aberration is the result of an adjacent 1:1 meiotic segregation of a maternal reciprocal translocation t(3,17)(p26.2;p13.3).

CONCLUSIONS

17p13.3 and 3p26 deletions have a clear range of phenotypic features while duplications still have an uncertain clinical significance. However, we could suggest that regardless of the type of the rearrangement, the gene dosage and interactions of CNTN4, CNTN6 and CHL1 in the 3p26 and PAFAH1B1, YWHAE in 17p13.3 could result in different clinical spectrums.