SMN2 and NAIP gene dosages in Vietnamese patients with spinal muscular atrophy

BACKGROUND

The SMN1 gene is now recognized as a spinal muscular atrophy (SMA)-causing gene, while SMN2 and NAIP have been characterized as a modifying factor of the clinical severity of SMA. Gene dosage of SMN2 is associated with clinical severity of SMA. But the relationship between gene dosage of NAIP and clinical severity of SMA remains to be clarified, although complete deletion of NAIP is frequent in type I patients.

METHODS

To evaluate the contribution of the SMN2 and NAIP gene dosages to SMA, quantitative real-time polymerase chain reaction was used to measure copy numbers of SMN2 and NAIP in 34 Vietnamese SMA patients lacking SMN1 (13 type I, 11 type II and 10 type III patients).

RESULTS

The SMN2 copy number in type I patients was significantly lower than that in type II-III patients, which was compatible with the previous reports. In contrast, 25 out of 34 patients had only zero or one copy of NAIP, while 50 out of 52 controls had two or more copies. For NAIP (+) genotype, six out of 13 type I patients, eight out of 11 type II patients and six out of 10 type III patients carried one NAIP copy.

CONCLUSIONS

The SMN2 copy number was related to the clinical severity of SMA among Vietnamese patients. The presence of one NAIP copy, that is, heterozygous NAIP deletion, was common in Vietnamese SMA, regardless of clinical phenotype.

Living with congenital adrenal hyperplasia in Vietnam: a survey of parents

OBJECTIVE

Congenital adrenal hyperplasia (CAH) has the potential to place an enormous burden on families in resource-poor countries, and the aim of this survey was to provide more specific insights into the difficulties faced by families living with CAH in Vietnam. It is hoped that this information will be used to ensure that future efforts to reduce the burden of CAH are as effective, sustainable and appropriate as possible.

DESIGN AND METHODS

A questionnaire-based needs assessment survey was offered to parents of children with CAH who were attending the Annual CAH Support Group Meeting held at the National Hospital of Pediatrics (NHP) in Hanoi, Vietnam, on 10th June 2005.

RESULTS

Fifty-three families responded to the questionnaire. Information pertaining to the purchase and use of medication to treat CAH, access to medical care, surgical treatment for girls, and a wide range of parental concerns was collected.

CONCLUSIONS

This survey highlights the heavy burden that CAH places on families in Vietnam, and provides significant insights into various initiatives that could well help ease this suffering. In particular, efforts must be made to ensure essential medication is affordably available, communication of important messages to parents is enhanced, local support groups encouraged, and early diagnosis and medical treatment of CAH optimized so as to reduce morbidity and mortality.

Co-occurrence of mutations in both dystrophin- and androgen-receptor genes is a novel cause of female Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder. Here, we report a novel mechanism for the occurrence of DMD in females. In a Vietnamese DMD girl, conventional PCR amplification analysis disclosed a deletion of exons 12-19 of the dystrophin gene on Xp21.2, with a karyotype of 46, XY. Furthermore, a novel mutation in the androgen-receptor gene on Xq11.2-q12 was identified in this girl, which led to male pseudohermaphroditism. Co-occurrence of mutations of these two genes constitutes a novel mechanism underlying female DMD.

Molecular genetic analyses of five Vietnamese patients with spinal muscular atrophy

Most patients with spinal muscular atrophy (SMA) have been reported to show homozygous deletion of the gene responsible for SMA, SMN1. However, whether SMA patients homozygous for the SMN1 deletion exist in Southeast Asian countries, including Vietnam, remains to be determined, because molecular genetic analyses of SMA patients from these countries have not been reported. In this preliminary study, we analyzed five Vietnamese SMA patients and found that SMN1 gene exons 7 and 8 were completely absent in one of them, a 6-month-old girl with hypotonic muscles. Thus, SMN1 deletion can be a cause of SMA in Vietnam, although other genetic abnormalities should be considered as etiological factors in many cases. In conclusion, we identified a homozygous deletion of the SMN1 gene in a Vietnamese SMA patient. Since the number of the patients analyzed in this study was very limited, it is too early to determine whether SMN1 deletion is not a main cause of SMA in Vietnam.

Unequal crossing-over between aldosterone synthase and 11beta-hydroxylase genes causes congenital adrenal hyperplasia

Congenital adrenal hyperplasia is one of the most frequently inherited diseases. It is characterized by a severe decline in cortisol secretion, which results in a compensatory increase in ACTH and consequent adrenal growth (hyperplasia). Here we describe the first case of 11beta-hydroxylase deficiency that is caused by an unequal cross-over of the genes encoding aldosterone synthase (CYP11B2) and 11beta-hydroxylase (CYP11B1). CYP11B1 and CYP11B2 are located on chromosome 8q24 approximately 45 kb apart from each other. The investigated genetic recombination deleted the normal alleles of the two genes and created a chimeric fusion gene, which consists of the promotor and exons 1 through 4 of the aldosterone synthase gene plus intron 4 through exon 9 of the 11beta-hydroxylase gene. This recombination event subordinates any remaining 11beta-hydroxylase activity of the chimeric enzyme to the control mechanisms of CYP11B2, the expression of which is mainly regulated by angiotensin II and K(+). Normally the 11beta-hydroxylase activity is controlled by ACTH. The existence of the CYP11B2/CYP11B1 chimera was discovered by means of a PCR method and was confirmed with a Southern blot. Furthermore, by applying a minigene expression method we demonstrated a point mutation in intron 3 (IVS3+16G-->T) of the patient's second 11beta-hydroxylase allele that radically diminishes proper splicing of the pre-mRNA by giving rise to a new, highly preferred donor splice site.