We report the draft genome of Brevundimonas diminuta strain XGC1, isolated from a tuberculosis-infected patient in Gujarat, India. This study also reveals that the B. diminuta XGC1 strain has acquired mutation to confer resistance to quinolone drugs.
β-Thalassemia is a genetic disease characterized by reduced or non-functionality of β-globin gene expression, which is caused due to a number of variations and indels (insertions and deletions). In this case study, we have reported a rare occurrence of compound heterozygosity of two different variants, namely, HBBc.92G > C and HBBc.92 + 5G > C in maternal amniotic fluid sample. Prenatal β-thalassemia mutation detection in fetal DNA was carried out using nucleotide sequencing method. After analysis, the father was found to be heterozygous for HBBc.92G > C (Codon 30 (G > C)) mutation which is β0 type and the mother was heterozygous for HBBc.92 + 5G > C (IVS I-5 (G > C)) mutation which is β+ type. When amniotic fluid sample was analyzed for β-globin gene (HBB), we found the occurrence of heterozygous allelic pattern for aforesaid mutations. This compound heterozygous state of fetus sample was considered as β+/β0 category of β thalassemia which was clinically and genotypically interpreted as β-thalassemia major. Regular blood transfusions are required for the survival of thalassemia major patients hence prenatal diagnosis is imperative for timely patient management. Prenatal diagnosis helps the parents to know the thalassemic status of the fetus and enables an early decision on the pregnancy. In the present study, we have identified compound heterozygosity for β-thalassemia in the fetus which portrays the importance of prenatal screening.
About 200 causative mutations are characterized in the β-globin gene. Beta thalassemia diagnosis is very complicated due to the genetic diversity of HBB gene across different geographical regions of the world. In the present study, we have analyzed 138 clinical specimens among them 66 were from 21 unrelated families (trio samples which had DNA from father, mother and chorionic villus sample/amniotic fluid sample) and 72 individual specimens using newly developed sequencing and PCR based assay. We observed 11 different HBB gene mutations in 138 samples, which were also cited by literature as the most prevalent mutations in Indian subcontinent population. The most common mutation observed in our study was HBB.C.92+5 G>C (GC+CC genotype was observed to be 44.93%). Few interesting case studies like co-inheritance of sickle cell anemia and β-thalassemia traits, compound heterozygosity of beta thalassemia major mutation in the case of twin pregnancy were also focused briefly. Commercially available molecular diagnostic kits of HBB gene can detect and identify targeted mutations but will not detect novel and non-targeted mutations of beta thalassemia in parental blood and fetal samples. Hence, a screening technique involving complete sequencing of HBB gene (β-globin gene) is required along with gap PCR approach to provide complete diagnosis of beta thalassemia disease.
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