Prenatal diagnosis of 22q11.2 copy number abnormalities in fetuses via single nucleotide polymorphism array

Pathogenic recurrent copy number variants in 7,078 pregnancies via chromosomal microarray analysis

OBJECTIVES

To investigate the incidence of pathogenic recurrent CNVs in fetuses with different referral indications and review the intrauterine phenotypic features of each CNV.

METHODS

A total of 7,078 amniotic fluid samples were collected for chromosome microarray analysis (CMA) and cases carrying pathogenic recurrent CNVs were further studied.

RESULTS

The highest incidence of pathogenic recurrent CNVs was 2.25 % in fetal ultrasound anomalies (FUA) group. Moreover, regardless of other indications, pregnant women with advanced maternal age have a lower incidence compared with whom less than 35 years old (p<0.05). In total 1.17 % (83/7,078) samples carried pathogenic recurrent CNVs: 20 cases with 22q11.2 recurrent region (12 microdeletion and eight microduplication), 11 with 1q21.1 (five microdeletion and six microduplication) and 16p13.11 (four microdeletion and seven microduplication), 10 with 15q11.2 recurrent microdeletion, seven with Xp22.31 recurrent microdeletion and 16p11.2 (three microdeletion and four microduplication), four with 7q11.23 (two microdeletion and two microduplication), three with 17p11.2 (three microdeletion), 17p12 (two microdeletion and one microduplication) and 17q12 (two microdeletion and one microduplication). The rest ones were rare in this study.

CONCLUSIONS

Pathogenic recurrent CNVs are more likely to be identified in FUA group. Pregnant women with advanced maternal age have a lower incidence of pathogenic recurrent CNVs. The profile of pathogenic recurrent CNVs between prenatal and postnatal is different, especially in 22q11.2, 1q21.1, 15q13.3 recurrent region and 15q11.2 deletion.

Prenatal phenotype of 22q11 micro-duplications: A systematic review and report on 12 new cases

The 22q11 region is prone to generating recurring Copy Number Variations (CNVs) as a result of the large numbers of Low Copy Repeats (LCRs). Typical duplications encompass the LCR-A-to-D region but atypical duplications of various sizes have also been reported. These duplications are responsible for highly variable phenotypes with incomplete penetrance and expressivity, which is challenging for adequate genetic counselling, especially in the prenatal period. To better delineate prenatal phenotypes associated with these CNVs, we report here a clinical and molecular description of twelve cases (9 foetuses and 3 deceased new-borns babies) carrying recurrent 22q11 duplications (diagnosed via aCGH), along with a review of the existing literature. 22q11 duplications were inherited from an apparently healthy parent in almost 60% of the cases. Other CNVs were diagnosed for 8% of the cases. Increased nuchal translucency and cardiac anomalies (CHD) were the most prominent phenotypes observed, along with mild renal and skeletal anomalies. Duplications encompassing the LCR-C-to-D region (and the CRKL gene) seemed more likely to generate CHDs and renal malformations. Cleft lip/palate were observed in foetuses with duplications encompassing the LCR-A-to-B region or the SPECC1L gene, as previously suggested. However, genotype-phenotype correlations remain difficult to ascertain. Second-hit point variants, epigenetic or environmental variations could play a role in the phenotypic variability of 22q11 duplications, but remain a challenge for assessment in the short period of pregnancy.