A 15-year-long Southern blotting analysis of FMR1 to detect female carriers and for prenatal diagnosis of fragile X syndrome in Taiwan.

Here, we review the results of Southern blotting analyses of the FMR1 gene performed in our reference laboratory in Taiwan over a 15-year period. In total, 725 high-risk women with a family history of fragile X syndrome (FXS) or idiopathic intellectual disability, 3911 low-risk pregnant women without such family history, and prenatal diagnosis data for 32 foetuses from 24 carrier mothers were included. Only 2 carriers were in the low-risk group, which indicated a prevalence of 1 of 1955 women (95% confidence interval: 1/7156-1/539). A total of 100 carriers were found to be in the high-risk group, thus revealing a significantly higher frequency than the low-risk group (100/725 vs 2/3911, P<0.0001). Eight of the 14 foetuses that inherited the maternal mutant allele were verified to have a full mutation, with the smallest maternal pre-mutation allele carrying 56 CGG repeats. The overall findings confirmed that the carrier prevalence among low-risk women in Taiwan is significantly lower than that reported in western countries. Therefore, the most important step for preventing FXS in Taiwan would be to focus on high-risk women by promoting general awareness of this disease and spreading knowledge regarding the benefits of carrier screening and prenatal testing.

A novel microdeletion at chromosome 2q31.1-31.2 in a three-generation family presenting duplication of great toes with clinodactyly.

HOXD gene cluster maps to chromosome 2q31 and plays a key role in embryonic limb morphogenesis. Mutations of the HOXD13 and HOXD10 genes have been found to be associated with digital and limb malformations. In addition, dysregulation of HOXD gene cluster has been proposed to account for the limb abnormalities in patients with chromosome 2q rearrangements. In this report, we investigated a three-generation family presenting clinical phenotypes of duplication of great toes, tapering fingers, and clinodactyly of the fifth finger in both hands, which were transmitted in a dominant fashion in this family. We identified and validated an interstitial microdeletion of approximately 3.4 Mb at chromosome 2q31.1-31.2 by array-based comparative genomic hybridization, fluorescence in situ hybridization, and real-time quantitative polymerase chain reaction that cosegregates with the clinical phenotypes in this family. The microdeletion removes 30 labeled genes including the entire HOXD gene cluster, suggesting that the digital abnormalities of this family may be attributed to the haploinsufficiency of the HOXD gene cluster. The delineation of the microdeletion region may contribute to the genotype-phenotype correlation study in patients with genomic rearrangements of the long arm of chromosome 2 and helps to understand the pathogenesis of haploinsufficiency of the HOXD gene cluster.

Contributions of bone maturation measurements to the differential diagnosis of neonatal transient hypothyroidism versus dyshormonogenetic congenital hypothyroidism.

AIM: To a) evaluate the contribution of bone maturation in the diagnosis of neonatal transient hypothyroidism versus dyshormonogenetic congenital hypothyroidism in full-term newborns, and b) use bone maturation to test the hypothesis that neonatal transient hypothyroidism is perinatal in onset. MATERIALS AND METHODS: The study included 20 patients with dyshormonogenetic and 43 with transient hypothyroidism. Thyroid function and measurements of the distal femoral epiphysis area, obtained at the time of first confirmatory diagnosis, were compared between the two groups. The epiphysis area in two control groups with normal thyroid function was also measured and compared with that in patients with transient hypothyroidism, at age 1-3 d (control A), or at the age when normal thyroid function was confirmed (control B). RESULTS: Mean epiphysis area was 0.04 cm2 in patients with dyshormonogenetic versus 0.22 cm2 in patients with transient hypothyroidism (p < 0.0001). An area <0.05 cm2 was limited to patients with dyshormonogenetic hypothyroidism. Conversely, a normal area (>0.2 cm2) was only observed in patients with transient hypothyroidism. Mean epiphysis areas in control A (0.20 cm2) and in patients with transient hypothyroidism were similar (p = 0.37), consistent with perinatal onset of transient hypothyroidism. Mean epiphysis area in control B (0.31 cm2) was significantly greater than in patients with transient hypothyroidism (p < 0.01). CONCLUSIONS: A short duration of hypothyroidism can significantly delay bone maturation. Examination of bone maturation at initial confirmatory evaluation yields important information pertaining to congenital hypothyroidism, not only to predict intellectual development, but also to evaluate the risk of dyshormonogenetic hypothyroidism.

An effective strategy of using molecular testing to screen mentally retarded individuals for fragile X syndrome.

Fragile X syndrome (FXS) is the most common form of familial mental retardation (MR). It is caused by the expansion of the CGG repeat in the FMR1 gene on the X chromosome. To date, FXS is not treatable, but can be prevented by prenatal genetic examination. Identifying women who carry a full mutation or premutation FMR1 gene is thus very important, and can be done by tracing family members of FXS subjects. However, most of the FXS subjects in Taiwan as well as those in many other countries have not been identified. In this study the authors attempt to develop reliable and inexpensive tests suitable for a large-scale screen of subjects with MR for FXS. Together with their previous study, a total of 311 male and 160 female subjects with MR were screened with nonradioactive Southern blot assay using mixed deoxyribonucleic acid from three subjects of the same sex. From these subjects, nine male subjects and one female FXS subject were diagnosed. All male subjects were also screened with nonradioactive polymerase chain reaction (PCR). These nine male FXS subjects were also detected on the basis of PCR amplification failure. No false-negative results were discerned. The PCR procedure was simplified further by combining it with an analysis of a blood spot on filter paper, which is a much simpler and cheaper method for sample collection and DNA preparation. This method was then used to screen 104 boys with MR. Two of them were suspected, and later confirmed with Southern blot assay, as subjects with FXS. This study suggests that simple PCR combined with blood spot analysis could be a reliable, inexpensive test that is feasible for a large-scale screening of male subjects with MR for FXS. However, Southern blot assay with mixed deoxyribonucleic acid is appropriate for screening female subjects. Based on this strategy, most FXS subjects could be identified easily for further management.

Bilateral ulnar hemimelia in Brachmann-de Lange syndrome: report of one case.

Twenty-three cases of Brachmann-de Lange syndrome (BDLS) have been reported in literature here in Taiwan, but none of them had severe upper limb anomalies. We report on a male infant with BDLS who has bilateral ulnar hemimelia.

EEG--a valuable tool in early diagnosis of Angelman syndrome.

Angelman Syndrome (happy puppet syndrome) is one of the genetic diseases causing developmental delay in children. Late diagnosis used to be the rule because of delayed appearance of disease markers such as craniofacial dysmorphism, ataxia, unprovoked laughter and seizure. However, reports have described characteristic EEG changes such as 2-3 Hz large amplitude slow wave paroxysms which appear early and are quite specific to the syndrome. With EEG aid, we made very early diagnosis in a 9 month-old young infant. And we would like to advocate the use of EEG study in cryptogenic psychomotor retardation in children.

An R248C mutation of FGFR3 leading to thanatophoric dysplasia type I.

Thanatophoric dysplasia (TD) is the most common form of lethal neonatal dwarfism with micromelic shortening of the limbs, macrocephaly, platyspondyly, and reduced thoracic cavity. R248C mutation in the extracellular domain of fibrobast growth factor receptor 3 (FGFR3) was common in TD type I. Two TD type I patients were examined for R248C mutation by use of restriction digestion and direct sequencing. The results showed that both patients carried R248C mutation. Because of the homogeneity of R248C mutation among different ethnic populations, all TD patients should be analysed using this PCR-based method presented in this work.

Arylsulfatase A pseudodeficiency in Chinese.

Arylsulfatase A (ASA) pseudodeficiency was found to be much rarer in Taiwan than in most western countries (2.5% versus 7.3%-20% carrier rate). The linkage of two mutations (A2725G and A1788G) in the pseudodeficiency allele was preserved in Chinese, and A2725G did not occur alone. This unusual linkage of mutations has not been fully explained previously because the frequency of A2725G alone was not clear (as low as 4% in the only report). However, A1788G was found in 55 of 160 (34.4%) DNA samples tested in this study. These data suggest that the A2725G mutation occurred in DNA that already contained the A1788G change, at an ancient time in one of our common ancestors.

Oculomotor apraxia in a case of Gaucher's disease with homozygous T1448C mutation.

We report a 10-month-old male infant with Type 2 Gaucher's disease. In addition to gradual arrest of neurological development, laryngospasm, opisthotonus, and limb rigidity, he presented characteristic oculomotor apraxia. History taking revealed that he had had abnormal horizontal gaze and had to turn his head to follow an object instead of moving the eyes alone. His eyes were in a divergent position while he was in a deep coma; however, when consciousness improved, he could open eyes with neutral eye position. Due to the impairment of reflex saccades, the doll's eye phenomenon was not reliable in evaluating the brainstem function when he was in the comatose stage. His leukocyte glucocerebrosidase activity was very low, but the typical Gaucher cell was absent in the sample of bone marrow aspiration. Molecular analysis by amplification refractory mutation system (ARMS) screening proved that he was a homozygote for T1448C mutation. To our knowledge, the T1448C gene frequency of Chinese Gaucher's disease is high. Thus, the ARMS screening method is applicable for further genetic diagnosis of Chinese Gaucher patients. Finally, this successful genetic diagnosis makes it possible in the future to perform prenatal diagnosis.