Identification of a Novel 7-bp Deletion in the α-Globin Gene Cluster in One Chinese Family.

Deletional α-thalassemia is characterized by reduced hemoglobin A2 and involves the deletion of a few nucleotides, which is a rare hereditary disease. However, the detection of rare mutations using commonly used genetic tests is highly challenging. In the present study, next-generation sequencing (NGS) was used to identify a novel 7-bp deletion α-thalassemia in one individual from a Chinese family. Hematological parameters of the family members were determined using an automated cell counter, and hemoglobin electrophoresis was performed using a capillary electrophoresis system. Subsequently, NGS was performed on the genomic DNA of the patient and her family members. The 7-bp deletion (named Hb Honghe [HBA1: c.401_407delGCACCGT]) of α-thalassemia in the α-globin gene was confirmed using Sanger sequencing. The patient's father was also a heterozygous carrier of HBA1: c.401_407delGCACCGT deletion, but not her mother or sister. The application of the combined molecular approach is essential for the accurate diagnosis of rare thalassemia. This study reports a novel case of α- thalassemia. The characterization of the mutation might provide new insights into genetic counseling and accurate diagnosis of thalassemia.

[Association of copy number of SMN1 and SMN2 with clinical phenotypes in children with spinal muscular atrophy].

OBJECTIVE: To study the association of copy number of SMN1 and SMN2 with clinical phenotypes in children with spinal muscular atrophy (SMA). METHODS: A total of 45 children with SMA were enrolled. Multiplex ligation-dependent probe amplification was used to measure the gene copy numbers of SMN1 and SMN2. The association of copy number of SMN1 and SMN2 with clinical phenotypes was analyzed. RESULTS: Of the 45 children with SMA, 42 (93%) had a homozygous deletion of SMN1 exons 7 and 8, and 3 (7%) had a deletion of SMN1 exon 7 alone. No association was found between SMA clinical types and the deletion types of SMN1 exons 7 and 8 (P>0.05). There was a significant difference in the distribution of SMN2 gene copy numbers between the children with SMA and the healthy children (P<0.05). The children with SMA usually had two or three copies of SMN2 gene, while the healthy children usually had one or two copies of SMN2 gene. There was a significant difference in the distribution of SMN2 copy numbers among the children with different SMA clinical types (P<0.05). The children with two copies of SMN2 gene had a significantly lower age of onset than those with three or four copies. Most of the children with type I SMA had two or three copies of SMN2 gene. Most of the children with type II SMA had three copies of SMN2 gene. Most of the children with type III SMA had three or four copies of SMN2 gene. Children with a higher copy number of SMN2 gene tended to have an older age of onset and better motor function and clinical outcome, and there was a significant association between SMN2 gene copy number and clinical outcome (P<0.05). CONCLUSIONS: The SMN2 gene can reduce the severity of SMA via the dosage compensation effect. SMN2 copy number is associated with the phenotype of SMA, and therefore, it can be used to predict disease severity.

[Gene Analysis of Thalassemia in Han and Dai Ethnic Childbearing-aged Population of Chinese Yunnan Province].

OBJECTIVE: To investigate the common mutation spectrum of α- and ß-thalassemia in Yunnan childbearing-aged population. METHODS: The common mutation types of α- or ß-globin genes were detected by multiple Gap-PCR and the PCR-reversed dot blotting, and the unknown mutation types were determined by DNA sequencing in DNA samples of hypochromic microcytic anemia patients and carriers who were confirmed to be positive by serologic screaning, then the mutation types of globin in Yunnan population were analyzed statistically. RESULTS: A total of 40 kinds of mutation types were detected in 685 detected persons, among them the 3 commonest mutation types of α-globin genes were --(SEA)/αα (49.09%), -α(3.7)/αα (36.67%) and α(CS)α/αα (8.79%), the 3 commonest genetypes of ß-globin gene were CD26(GAG>AAG)/N (43.78%), CD41-42(-CTTT)/N (20.1%) and CD17(AAG>TAG)/N (18.9%). There were 348 Han and 212 Dai ethnic persons in 685 cases, but their mutation of globin genes were different between these 2 ethnic groups. The results also showed that the gene mutation types were mostly concentrated in Dai ethnic individuals, since 28 of 38 detected α-ß-thalassemia cases were Dai ethnic individuals. CONCLUSION: The mutation spectrums of α- and ß-globin genes in Yunnan childbearing-aged population are diverse and different from that in other areas of China.