Yoshinori Izumikawa

Replication asynchrony between homologs 15q11.2 cytogenetic evidence for genomic imprinting

SummaryReplication kinetics of the Prader-Willi syndrome critical region (15q11.2) was investigated in seven normal healthy adult females using RBG replication bands. Replication asynchrony between homologs 15q11.2 was identified consistently in about 40% of cells in all individuals. It was limited to the stages in which Xp22, Xp11, Xq13 and Xq24/26 were visible in the late-replicating X chromosome. This asynchrony suggested that replication timing overlapped between 15q11.2 and the early replicating R-bands of the late X chromosome in some cells, and that the difference in replication timing between homologs was probably related to genomic imprinting; the latter has been suggested as a pathogenetic basis of Prader-Willi syndrome. As a result of an analysis of the proportions of asynchronous and synchronous cells in each replication stage, two types of cells were deduced providing 1∶1 methylation mosaicism of genomic imprinting was assumed. The first type was composed of cells with normal replication in one homolog and delayed replication in the other. The second type was composed of cells with normal replication in both homologs. Our results provide cytogenetic evidence of methylation mosaicism for mammalian genomic imprinting.

The costello syndrome: A boy with thick mitral valves and arrhythmias

SummaryA 3-year-old boy with Costello syndrome is reported. He had typical clinical features of the syndrome including severe postnatal growth retardation, poor sucking, mild developmental delay, a coarse characteristic facies, thick and loose skin of the hands and feet, sparse and curly hair, dark skin, and relative macrocephaly but lacked nasal papillomas. In addition, he had cardiac anomalies with extrasystoles and thick mitral valve tips. Mitral valve defects may be a clinical feature of the syndrome.

Trisomy 9q3 syndrome: a case report and review of the literature

A girl with partial trisomy 9q is reported. She was characterized by dolichomorphism, abnormalities of the digits, a cardiac defect and craniofacial dysmorphism. A high‐resolution analysis revealed the karyotype to be: 46,XX,‐3,+der(3)t(3;9)(q29;q13) de novo. A phenotype‐karyo‐type correlation study in 22 cases of partial trisomies 9q supported the delineation of a trisomy 9q3 syndrome. The smallest region of overlap was confined to 9q32.

16q21 Is critical for 16q deletion syndrome

A 1‐year‐old girl with an interstitial deletion of the long arm of chromosome 16 is reported. She was characterized by a distinct craniofacial dysmorphism, meningoencephalocele, mild hydrocephalus, short neck, broad great toes and abnormally positioned toes. High resolution GTG and RBG banding analyses revealed a karyotype: 46,XX,del(16) (q13q22) de novo. An analysis of the smallest region of overlap revealed that the critical band region for 16q deletion syndrome is 16q21.

Two sisters with Toriello-Carey syndrome

Toriello-Carey syndrome comprises agenesis of the corpus callosum, telecanthus, short palpebral fissures, small nose with anteverted nares, Robin sequence, abnormally shaped ears, cardiac defect, and hypotonia. We describe two Japanese sisters with a Toriello-Carey syndrome whose phenotypes were as severe as reported male cases. The younger sister died suddenly at age 4 months. Our patients with a severe phenotype and possible parental consanguinity suggest autosomal recessive inheritance of Toriello-Carey syndrome.

Small interstitial deletion of the long arm of chromosome 2 (2q24.3): further delineation of 2q medial monosomy syndrome.

SummaryWe report on a female infant with an interstitial deletion involving 2q24.3. She had multiple congenital anomalies similar to those in patients with del(2)(q31q33) except for an occipital encephalocele. As a result of comparison of clinical findings among interstitial 2q deletions, a distinct 2q medial monosomy syndrome may be delineable in association with a deletion of 2q31.

Gene assignment of Zellweger syndrome to 7q11.23: report of the second case associated with a pericentric inversion of chromosome 7

SummaryThe case of a newborn girl with Zellweger syndrome and a pericentric inversion of chromosome 7, 46,XX, inv(7)(p12q11.23), is reported. The diagnosis was confirmed by marked deficiency of peroxisomal beta-oxidation enzymes in hepatic cells from autopsy samples. This is the second case of Zellweger syndrome associated with a rearrangement of chromosome 7, the tentative gene assignment to 7q11 being further supported; the gene is probably confiend to 7q11.23.

Sanfilippo type B syndrome: five patients with an R565P homozygous mutation in the α-N-acetylglucosaminidase gene from the Okinawa islands in Japan

AbstractSanfilippo type B syndrome (mucopolysaccharidosis type IIIB; MPS IIIB) is an autosomal recessive lysosomal storage disorder that is caused by defective α- N-acetylglucosaminidase (NAGLU). We performed NAGLU gene analysis in five patients with MPS IIIB whose respective parents from the Okinawa islands in Japan were not apparently consanguineous. We found a missense mutation (R565P) in all five patients (all homozygotes). We screened this mutation in 200 healthy subjects and found one heterozygote (none of the subjects were related to the patients). These results suggest that there may be a founder effect that results in the accumulation of R565P mutation in this area.

Characterization of marker chromosomes by fish using microdissected probes from old carnoy-fixed cells: Report of two cases

SummaryWe reported on two patients with a de novo marker chromosome of which the origins were successfully identified by FISH using microdissected probes. These probes were established by microdis-sections of extra chromosomal segments from Carnoy-fixed cells stored at −20°C for several years. Using these probes, we could verify partial 1q32 trisomy in a patient with 17p+ as well as partial 16q2 trisomy in another patient with 4p+.

Application of personal computer to an analysis of small de novo chromosomal insertion: A case of de novo 3q2 trisomy with ins(8;3)

SummaryTo identify the origin of a small inserted segment in a de novo 8p+ chromosome, an originally programmed computerized data-base for chromosomal aberration syndromes was utilized. The system selected 3q2 trisomy and 10q2 trisomy as candidates. As a result of a careful comparison of several high-resolution banding patterns among chromosomes 3, 10 and the inserted segment, her karyotype was disignated as: 46,XX,−8,+der(8), inv ins(8;3)(p21.1;q26.32q24) de novo. A small segment from 3q24 to 3q26.32 was trisomic, and invertedly inserted into the short arm of chromosome 8. This computerized database was considered to be useful for analyses of the small de novo inserted chromosomal segment.