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Biomedical subjects

M H Yong

Publications and source records attributed to M H Yong.

9 recordsLinked to original sources
PubMed1998

Highly complex chromosomal rearrangement of chromosome 9 in a case of chronic myeloid leukemia.

A 63-year-old man with chronic myeloid leukemia (CML) was found to have a new complex Philadelphia translocation. All of the bone marrow cells had a rearrangement of a five-way translocation, t(9;22;10;12;1), involving a single chromosome 9. The patient went into blast crisis two years after initial diagnosis and the karyotype remained unchanged. He died in blast crisis 10 months later. We believe this case is a unique 5-way translocation in which four chromosomes were translocated to a single chromosome.

Chromosomes, Human, Pair 1↗
PubMed1997

Partial monosomy for chromosome 22 in a girl with mental retardation.

This report describes a 5-year 6-month-old Chinese girl with partial monosomy for the long arm of chromosome 22. The karyotype was 46,XX/46,XX,del (22) (q13.2). She presented with global developmental delay. Clinical features include seizures, failure-to-thrive, prominent ears, long philtrum and abnormal skin pigmentation on the face and limbs.

Child, Preschool↗
PubMed1997

Williams syndrome--the Singapore General Hospital experience.

Williams syndrome first described in 1961 is generally characterised by mental deficiency, gregarious personality, unusual "elfin" facies, supravalvular aortic stenosis and idiopathic infantile hypercalcaemia. Patients with Williams syndrome show a hemizygous submicroscopic deletion of 7q11.23 detectable by fluorescent in-situ hybridisation (FISH). The deleted portion of the chromosome corresponds to the Elastin gene. We report 3 girls with characteristics of Williams syndrome in whom the diagnosis was confirmed by demonstration of the hemizygous deletion of 7q11.23 in the karyotype by FISH. These patients, aged 6, 7 and 10 years, showed the characteristic facies and gregarious personalities. Some developmental delay with mild mental deficiency and dysmorphic facies were prominent features in the initial presentation. Cardiac lesions found in these patients were small patent ductus arteriosus which closed, pulmonary valvular stenosis and mitral valve prolapse associated with mitral regurgitation respectively. Hypercalcaemia was not documented in these patients. Learning difficulty was a major issue and all patients required special schooling. Chromosome analyses done on peripheral blood were found to be normal in all patients. FISH using the Elastin Williams Syndrome Chromosome Region (WSCR) probes (oncor) showed the hemizygous deletion of 7q11.23. Diagnosis of Williams syndrome can now be confidently confirmed with the help of FISH.

Child↗
PubMed1996

Subtle translocation (18;21) confirmed by FISH in a patient with Down syndrome.

The patient presented with the typical features of Down syndrome; hypotonia, brachycephaly, flattened occiput, bilateral prominent medical epicanthic folds, flat nasal bridge, protruding tongue, low-set dysplastic ears, short broad hands, bilateral clinodactyly and simian crease. The karyotype of this child was originally reported as normal. High-resolution chromosomes revealed extra material on the long arm of chromosome 18. The mother's karyotype showed a reciprocal translocation between the long arm of 18 and the long arm of 21 at band q23 and q22.1, respectively. FISH performed separately with two different 21q cosmid probes gave two signals on the mother's metaphases and three signals on the proband. These findings confirmed that the proband is trisomic for the long arm of chromosome 21 at loci D21S65 and D21S19.

Chromosomes, Human, Pair 18↗
PubMed1995

Del(3) (p25.3) without phenotypic effect.

A terminal deletion of chromosome 3 at p25.3 was observed during prenatal diagnosis. A similar deletion is also present in the phenotypically normal mother. The deletion was confirmed by FISH. The breakpoint is distal to the region responsible for the 3p- syndrome. A normal baby girl was born with no apparent phenotypic abnormalities.

Adult↗
PubMed1990

Minimal sequence requirements for the regulated expression of rbcS-3A from Pisum sativum in transgenic tobacco plants.

RbcS-3A, the most highly expressed member of the pea multigene family encoding the small subunit of ribulose 1,5-bisphosphate carboxylase, is expressed in a light-dependent and organ-specific manner. In order to further delineate the sequences which mediate this complex pattern of regulation, putative regulatory sequences were assayed for function in transgenic tobacco plants in the context of an inactive 5' deleted rbcS-3A test gene. We have identified a minimal functional unit of 58 bp which is able to confer organ-specific transcriptional activity. It contains two sequences conserved among the pea rbcS family members, namely box II (-151 to -138; GTGTGGTTAATATG) and box III (-125 to -114; ATCATTTTCACT). These sequences bind the nuclear factor termed GT-1 in vitro. Substitution mutations within this 58 bp element have demonstrated that sequences upstream of, or located between, boxes II and III are not required for the transcriptional activity conferred by this element. Distance and orientation of these sequences from the gene are not critical for activity within the limits tested. DNA fragments upstream of nucleotide -170 of rbcS-3A that contain other GT-1 binding sites can also confer regulated expression upon the rbcS-3A promoter deleted to -50. Multimers of individual motifs, namely four tandem copies of boxes II and III, are unable to drive expression of the deleted promoter. These observations suggest that while GT-1 binding is necessary for promoter activity it is by itself not sufficient.

Base Sequence↗
PubMed1988

Binding site requirements for pea nuclear protein factor GT-1 correlate with sequences required for light-dependent transcriptional activation of the rbcS-3A gene.

Nuclear protein factor GT-1 binds to sequence boxes II, III, II* and III* upstream of the light-responsive pea rbcS-3A gene. We have shown previously that box II and box III are required for expression of rbcS-3A when redundant elements upstream of -170 (relative to the transcription start site) are removed. Here we present evidence that deletion and substitution mutations downstream of -170 which eliminate expression also decrease binding. Using a series of 2 bp substitution mutations we have defined a core of six residues (GGTTAA) within box II (GTGTGGTTAATATG) that are critical for binding. The most detrimental mutation for binding, which changes the double Gs to Cs, is sufficient to eliminate detectable expression in vivo when only 170 bp of 5' flanking sequences are present. The simplest interpretation of these data is that GT-1 is an activator of rbcS-3A transcription. Footprinting experiments show that GT-1 from both light-grown and dark-adapted plants binds to the same sequences in vitro. Therefore, the lack of expression of rbcS-3A in the dark is not due to the absence of GT-1. In our analysis of the sequence elements upstream of -170, we have mapped two additional GT-1 sites (boxes II** and III**) between -330 and -410. The similarities and differences among the GT-1 sites located upstream and downstream of -170 are discussed in terms of the different sequence requirements for rbcS-3A expression during development.

Base Sequence↗
PubMedDate not supplied

Tissue-limited mosaicism in Pallister-Killian syndrome -- a case in point.

We report a case of Pallister-Killian syndrome in a term female infant. Antenatal ultrasound showed left diaphragmatic hernia and polyhydramnios. She was ventilated from birth and the diaphragm defect repaired on day 5. She had dysmorphic features, including median cleft palate, patchy frontotemporal alopecia, hypopigmented skin whorls, and bilateral profound sensorineural hearing loss. Fetal and postnatal karyotypes of peripheral lymphocytes were both normal, 46, XX. Subsequently, a skin fibroblast culture showed mosaic tetrasomy of isochromosome 12p both on G-banding and fluorescence in situ hybridization, consistent with Pallister-Killian syndrome. This case illustrates the importance of using the appropriate sample type for karyotype analysis with implications for prenatal and postnatal diagnosis.

Abnormalities, Multiple↗