title: R133C and R168X mutations in Japanese Rett syndrome patients: a caution for misdiagnosis.
abstract: Rett syndrome is a neurodevelopmental disorder characterized by regression of motor and mental abilities in females after a period of normal development. The gene, MECP2, has been reported to be responsible for Rett syndrome. Here, we report the cases who were at first misdiagnosed as having homozygous mutations, and later corrected as heterozygous ones. We analyzed the MECP2 gene in three sporadic Japanese patients with Rett syndrome. Direct sequencing by using a primer set that was originally used in the first report of MECP2 mutation suggested two types of homozygous mutations (R133C and R168X). Previous reports of these mutations with heterozygous status, as well as the general nature of dominant inheritance in Rett syndrome females and lethality in hemizygous males, urged us to confirm the homozygosity of these mutations. By using a newly designed PCR primer, we found that these mutations actually occurred heterozygously in these patients. Sequence analyses of PCR products suggested that a C/T polymorphism found upstream of these mutations caused the preferential PCR amplification of the mutated alleles. These results recommend paying attention to biased PCR amplification that may lead to misjudgment of the result for mutational analysis of the MECP2 gene.
authors.affiliation: Laboratory for Neurogenetics, Brain Science Institute, The Institute of Physical and Chemical Research (RIKEN), 2-1, Hirosawa, Wako-shi, 351-0198, Saitama, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Amano
authors.forename: Y
authors.initials: Y
authors.lastname: Nomura
authors.forename: M
authors.initials: M
authors.lastname: Segawa
authors.forename: K
authors.initials: K
authors.lastname: Yamakawa
mesh_terms: D000293:Adolescent; D000328:Adult; D015139:Blotting, Southern; D002648:Child; D002675:Child, Preschool; D002868:Chromosomal Proteins, Non-Histone; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D005787:Gene Frequency / Q000235:genetics; D005820:Genetic Testing; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan; D008297:Male; D051783:Methyl-CpG-Binding Protein 2; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D012097:Repressor Proteins; D015518:Rett Syndrome / Q000175:diagnosis* / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2; D012097:Repressor Proteins