Rare nasal cleft in a patient with holoprosencephaly due to a mutation in the ZIC2 gene

Clinical application of chromosomal microarray analysis for fetuses with craniofacial malformations

Background

The potential correlations between chromosomal abnormalities and craniofacial malformations (CFMs) remain a challenge in prenatal diagnosis. This study aimed to evaluate 118 fetuses with CFMs by applying chromosomal microarray analysis (CMA) and G-banded chromosome analysis.

Results

Of the 118 cases in this study, 39.8% were isolated CFMs (47/118) whereas 60.2% were non-isolated CFMs (71/118). The detection rate of chromosomal abnormalities in non-isolated CFM fetuses was significantly higher than that in isolated CFM fetuses (26/71 vs. 7/47, p = 0.01). Compared to the 16 fetuses (16/104; 15.4%) with pathogenic chromosomal abnormalities detected by karyotype analysis, CMA identified a total of 33 fetuses (33/118; 28.0%) with clinically significant findings. These 33 fetuses included cases with aneuploidy abnormalities (14/118; 11.9%), microdeletion/microduplication syndromes (9/118; 7.6%), and other pathogenic copy number variations (CNVs) only (10/118; 8.5%).We further explored the CNV/phenotype correlation and found a series of clear or suspected dosage-sensitive CFM genes including TBX1, MAPK1, PCYT1A, DLG1, LHX1, SHH, SF3B4, FOXC1, ZIC2, CREBBP, SNRPB, and CSNK2A1.

Conclusion

These findings enrich our understanding of the potential causative CNVs and genes in CFMs. Identification of the genetic basis of CFMs contributes to our understanding of their pathogenesis and allows detailed genetic counselling.

Nasal fistula, epidermal cyst and hypernatremia in a girl presenting holoprosencephaly due to a rare ZIC2 point mutation

Holoprosencephaly is the most common brain malformation in humans and it is a complex genetic disorder. We report on a patient with holoprosencephaly caused by a rare ZIC2 mutation presenting a bifid nose associated with a nasal fistula and an epidermal cyst, besides hypernatremia. The patient was a 1 year and 4 months old girl that developed an important neuropsychomotor delay. Currently, she uses a wheelchair to move around and only emits sounds. Computed tomography (CT) scan revealed a semilobar holoprosencephaly and a Dandy-Walker variant. Head magnetic resonance imaging also disclosed corpus callosum agenesis and prefrontal subarachnoid space enlargement. On physical examination at 1 year and 4 months of age, we verified growth retardation, microcephaly, bilateral epicantic fold, upslanting palpebral fissures, bifid nose, and limbs spasticity secondary to hypertonia. Later, she began to present hypernatremia; however, its precise cause was not identified. At 6 years and 10 months of age, a nasal fistula was suspected. Facial CT scan showed an epidermal cyst at cartilaginous portion of the nasal septum. High resolution GTG-Banding karyotype was normal. However, molecular analysis through direct sequencing technique showed a mutation at regulatory region of the ZIC2 gene: c.1599*954T > A, a genetic variation previously described only in a Brazilian patient. Our patient presented findings still not reported in literature among patients with holoprosencephaly, including those with ZIC2 mutations. Thus, the spectrum of abnormalities associated to ZIC2 mutations may be broader and include other defects as those observed in our patient.

Case report: a novel mutation in ZIC2 in an infant with microcephaly, holoprosencephaly, and arachnoid cyst

RATIONALE

Holoprosencephaly (HPE) is a severe congenital brain malformation resulting from failed or incomplete forebrain division in early pregnancy.

PATIENT CONCERNS

In this study, we reported a 9-month old infant girl with mild microcephaly, semilobor HPE, and arachnoid cyst.

DIAGNOSES

Potential genetic defects were screened directly using trio-case whole exome sequencing (WES) rather than traditional karyotype, microarray, and Sanger sequencing of select genes.

OUTCOMES

A previous unpublished de novo missense mutation (c.1069C >G, p.H357D) in the 3rd zinc finger domain (ZFD3) of the ZIC2 gene was identified in the affected individual, but not in the parents. Sanger sequencing using specific primers verified the mutation. Extensive bioinformatics analysis confirmed the pathogenicity of this extremely rare mutation. Phenotype-genotype analysis revealed significant correlation between the 3rd zinc-finger domain with semilobor HPE.

LESSONS

These findings expanded the spectrum of the ZIC2 gene mutations and associated clinical manifestations, which is the first identification of a mutated ZIC2 gene in a Han infant girl with mild microcephaly, semilobor HPE, and arachnoid cyst.

Molecular analysis of holoprosencephaly in South America

Holoprosencephaly (HPE) is a spectrum of brain and facial malformations primarily reflecting genetic factors, such as chromosomal abnormalities and gene mutations. Here, we present a clinical and molecular analysis of 195 probands with HPE or microforms; approximately 72% of the patients were derived from the Latin American Collaborative Study of Congenital Malformations (ECLAMC), and 82% of the patients were newborns. Alobar HPE was the predominant brain defect in almost all facial defect categories, except for patients without oral cleft and median or lateral oral clefts. Ethmocephaly, cebocephaly, and premaxillary agenesis were primarily observed among female patients. Premaxillary agenesis occurred in six of the nine diabetic mothers. Recurrence of HPE or microform was approximately 19%. The frequency of microdeletions, detected using Multiplex Ligation-dependant Probe Amplification (MLPA) was 17% in patients with a normal karyotype. Cytogenetics or QF-PCR analyses revealed chromosomal anomalies in 27% of the probands. Mutational analyses in genes SHH, ZIC2, SIX3 and TGIF were performed in 119 patients, revealing eight mutations in SHH, two mutations in SIX3 and two mutations in ZIC2. Thus, a detailed clinical description of new HPE cases with identified genetic anomalies might establish genotypic and phenotypic correlations and contribute to the development of additional strategies for the analysis of new cases.