De Novo Mutated TUBB2B Associated Pachygyria Diagnosed by Medical Exome Sequencing and Long-Range PCR.

INTRODUCTION: A range of cerebrocortical development malformations (MCD) ranging from simplified gyral patterns to the complete loss of gyri and sulci is associated with mutations in a cluster of highly homolog ß-tublin genes, such as TUBB2A and TUBB2B. CASE REPORT: The fetus had pachygyria, asymmetrical perisylvian polymicrogyria, dysplasia of the lateral sulcus and insula, agenesis of the splenium and partial agenesis of the body corpus callosum, cerebellar superior vermian hypoplasia with agenesis of the inferior vermis. Karyotype and microarray were normal. Trio Medical Exome Sequencing detected a de novo novel heterozygous mutation c.862G > A (p.E288K) in the tubulinpathy genes. Long-range PCR and Sanger sequencing specific for TUBB2A and TUBB2B gene detected a heterozygous variant c.862G > A specific to TUBB2B. CONCLUSION: The combination of LR-PCR amplification and medical exome sequencing allows mutational assessment in tubulinopathy genes. Our study expands the spectrum of malformations associated with mutations in the ß-tubulin gene TUBB2B.

UPD16 itself is not a cause of intrauterine growth restriction.

BACKGROUND: The clinical relevance of uniparental disomy (UPD16) for chromosome 16 is currently unclear. METHODS AND RESULT: We performed chromosome microarray analysis on two fetus and their placentas, fluorescence in situ hybridization (FISH) to exclude the hidden chr16 trisomy mosaicism in the fetuses, and clinical whole-exome sequencing to assess for homozygosity mutations of autosomal-recessive diseases. RESULTS: Microarray analysis of two fetuses had UPD16. The membranous placenta of the case 1 had confined placental mosaicism (CPM) for trisomy 16. Clinical whole-exome sequencing on chromosome 16 revealed three potentially pathogenic single nucleotide polymorphisms (SNPs). Gap-polymerase chain reaction (PCR) and MLPA for a-thal deletions demonstrated that case 2 was homozygous for the -SEA deletion. CONCLUSIONS: The poor outcome in these fetuses may be attributed to other factors, the membranous placenta and the -SEA deletion, respectively. Fetal UPD16 itself might be not correlated with intrauterine growth restriction (IUGR) and thus is not the basic cause of IUGR.

[Analysis of a mistake occurring during prenatal diagnosis of two couples respectively carrying CD41-42 (-TCTT) and CD43(G>T) mutations of the beta hemoglobin gene].

OBJECTIVE: To provide prenatal diagnosis for two couples who respectively carried heterozygous CD41-42 (-TCTT) and CD43 (G>T) mutations of the beta hemoglobin gene. METHODS: The mutations were simultaneously detected with reverse dot blot (two diagnostic kits), multi-color melting curve analysis and sequencing analysis. RESULTS: The fetus of family 1 was shown to be heterozygous for CD43 (G>T) by the three methods, while the fetus of family 2 was shown to be double heterozygous for CD41-42 (-TCTT) and CD43 (G>T) by multi-color melting curve analysis and sequencing analysis. The two diagnostic kits yielded different results by reverse dot blot, one as double heterozygous for CD41-42 (-TCTT) and CD43 (G>T), and another as homozygous for CD41-42 (-TCTT). CONCLUSION: For prenatal diagnosis of couples carrying mutations of beta hemoglobin gene such as CD41-42 (-TCTT) and CD43 (G>T), other methods such as Sanger sequencing should be used in order to avoid misdiagnosis.

[Application of multiplex ligation-dependent probe amplification technique in prenatal diagnosis of α-thalassemia].

OBJECTIVE To assess the application value of multiplex ligation-dependent probe amplification (MLPA) for the detection of gene deletion and prenatal diagnosis of α-thalassemia. METHODS MLPA was applied for 2 cases with α-thalassemia phenotype by whole blood cell counting and hemoglobin component detection but were ruled out by regular molecular diagnosis. Potential gene deletions and point mutations of α-thalassemia gene were detected with regular Gap-polymerase chain reaction (Gap-PCR) and reverse dot blotting (RDB) in 89 cases where one or both partners were carriers of α-thalassemia mutations. Meanwhile, MLPA was used for detecting α-globin gene deletion among the 89 samples. RESULTS For the 2 cases with α-thalassemia phenotype, no α globin gene deletion was detected by MLPA, but were subsequently confirmed as iron-deficiency anemia. The results of MLPA and Gap-PCR detection for the 88 cases were consistent, except for 1 fetal sample (chorionic villi) which could not be diagnosed by Gap-PCR and was confirmed to be - SEA/αα by MLPA. CONCLUSION MLPA can be applied to prenatal diagnosis of α-thalassemia as an effective supplement to Gap-PCR to reduce both misdiagnosis and missed diagnosis and improve the accuracy of prenatal diagnosis.