Identification in Chinese patients with GLIALCAM mutations of megalencephalic leukoencephalopathy with subcortical cysts and brain pathological study on Glialcam knock-in mouse models.

BACKGROUND: Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare neurological degenerative disorder caused by the mutations of MLC1 or GLIALCAM with autosomal recessive or autosomal dominant inheritance and a different prognosis, characterized by macrocephaly, delayed motor and cognitive development, and bilateral abnormal signals in cerebral white matter (WM) with or without cysts on magnetic resonance imaging (MRI). This study aimed to reveal the clinical and genetic features of MLC patients with GLIALCAM mutations and to explore the brain pathological characteristics and prognosis of mouse models with different modes of inheritance. METHODS: Clinical information and peripheral venous blood were collected from six families. Genetic analysis was performed by Sanger sequencing of GLIALCAM. GlialcamArg92Trp/+ and GlialcamLys68Met/Thr132Asn mouse models were generated based on mutations from patients (c.274C>T(p.Arg92Trp) (c.203A>T(p.Lys68Met), and c.395C>A (p.Thr132Asn))). Brain pathologies of the mouse models at different time points were analyzed. RESULTS: Six patients were clinically diagnosed with MLC. Of the six patients, five (Pt1-Pt5) presented with a heterozygous mutation in GLIALCAM (c.274C>T(p.Arg92Trp) or c.275G>C(p.Arg92Pro)) and were diagnosed with MLC2B; the remaining patient (Pt6) with two compound heterozygous mutations in GLIALCAM (c.203A>T (p.Lys68Met) and c.395C>A (p.Thr132Asn)) was diagnosed with MLC2A. The mutation c.275C>G (p.Arg92Pro) has not been reported before. Clinical manifestations of the patient with MLC2A (Pt6) progressed with regression, whereas the course of the five MLC2B patients remained stable or improved. The GlialcamArg92Trp/+ and GlialcamLys68Met/ Thr132Asn mouse models showed vacuolization in the anterior commissural WM at 1 month of age and vacuolization in the cerebellar WM at 3 and 6 months, respectively. At 9 months, the vacuolization of the GlialcamLys68Met/ Thr132Asn mouse model was heavier than that of the GlialcamArg92Trp/+ mouse model. Decreased expression of Glialcam in GlialcamArg92Trp/+ and GlialcamLys68Met/ Thr132Asn mice may contribute to the vacuolization. CONCLUSIONS: Clinical and genetic characterization of patients with MLC and GLIALCAM mutations revealed a novel mutation, expanding the spectrum of GLIALCAM mutations. The first Glialcam mouse model with autosomal recessive inheritance and a new Glialcam mouse model with autosomal dominant inheritance were generated. The two mouse models with different modes of inheritance showed different degrees of brain pathological features, which were consistent with the patients' phenotype and further confirmed the pathogenicity of the corresponding mutations.

[Epidemiological study on developmental delay of 18-month-old children from four districts/counties in Beijing].

OBJECTIVE: To investigate epidemiological characteristics of prevalence, impact factors and etiology on developmental delay of 18-month-old children from four districts/counties in Beijing. METHODS: An epidemiological study on developmental delay was designed to investigate all the 18-month-old children enrolled from Shunyi,Daxing,Miyun and Yanqing districts/counties in Beijing from May to September, 2011. Combining the tertiary network of child health with hospital clinical study was used. Child developmental questionnaires were completed by doctors in communities of the first network of child health. Gesell Developmental Schedules for children with Denver developmental screening test (DDST) screening positive results were assessed by doctors in districts/counties hospitals of the second network of child health. The children diagnosed as developmental delay were transferred to the tertiary hospitals of the third network of child health for further etiological diagnosis, follow-up and developmental evaluation. The case-control study compared between children with/without developmental delay were performed in accordance with the 1:4 ratios by gender and residence community matched. SPSS 16.0 was adopted for data analysis of the case-control study. RESULTS: A total of 3 182 children were screened among the 4 037 children fitting the criteria,and the coverage rate was 78.8% (3 182/4 037). Of the 3 182 screened children, 22 children were diagnosed as developmental delay. The prevalence rate was 6.91 ‰ (22/3 182). Out of the 22 children with developmental delay, 15 were boys and 7 were girls. The sex ratio was 2.1:1. The prevalence rates of the children with developmental delay in Shunyi, Daxing, Miyun and Yanqing were 3.45 ‰ (4/1 160), 4.50 ‰(5/1 111), 15.87 ‰(7/441) and 12.77 ‰ (6/479), respectively. The results from one-way ANOVA analysis showed the main risk factors in children with developmental delay included low-income families, mothers' low educational level, small size for gestational age infant, multiple fetuses, serious diseases after birth, congenital malformations and physical retardation (P<0.05). CONCLUSION: The screening coverage rate of this study is 78.8%. The prevalence rate of children with developmental delay is 6.91 ‰, which is significantly different in sex ratio and districts of the subjects. The etiology of developmental delay might be associated with social-economic and biological factors.

[Analysis of HEPACAM mutations in a Chinese family with megalencephalic leukoencephalopathy with subcortical cysts].

OBJECTIVE: To explore HEPACAM mutations in a Chinese family with megalencephalic leukoencephaloptathy with subcortical cysts (MLC). METHOD: Genomic DNA samples were extracted from peripheral blood of the proband and her parents. All exons and exon-intron boundaries of HEPACAM and MLC1 were amplified in the MLC family by polymerase chain reaction (PCR) followed by direct DNA sequencing. RESULT: Two heterozygous mutations of HEPACAM located in exon 2, c.203A > T(p.K68M) and c.395C > A(p.T132N), were identified in the proband. The proband's mother had the heterozygous mutations c.203A > T(p.K68M), and her father had the heterozygous mutation-c.395C > A(p.T132N). There was no variation found in MLC1 gene. CONCLUSION: The proband was heterozygous compound MLC patient carrying on one allele with the c.203A > T(p.K68M) mutation inherited from her mother, and the other allele with the c.395C > A(p.T132N) mutation inherited from her father. The parents both are heterozygous carriers with normal phenotype. The disease-causing gene for this family was resulted in HEPACAM mutation other than MLC1 mutation.