Biomedical subjects

Susanna Chan

Publications and source records attributed to Susanna Chan.

7 recordsLinked to original sources

PubMed2006

Oligonucleotide microarray analysis of genomic imbalance in children with mental retardation.

The cause of mental retardation in one-third to one-half of all affected individuals is unknown. Microscopically detectable chromosomal abnormalities are the most frequently recognized cause, but gain or loss of chromosomal segments that are too small to be seen by conventional cytogenetic analysis has been found to be another important cause. Array-based methods offer a practical means of performing a high-resolution survey of the entire genome for submicroscopic copy-number variants. We studied 100 children with idiopathic mental retardation and normal results of standard chromosomal analysis, by use of whole-genome sampling analysis with Affymetrix GeneChip Human Mapping 100K arrays. We found de novo deletions as small as 178 kb in eight cases, de novo duplications as small as 1.1 Mb in two cases, and unsuspected mosaic trisomy 9 in another case. This technology can detect at least twice as many potentially pathogenic de novo copy-number variants as conventional cytogenetic analysis can in people with mental retardation.

Child↗

PubMed2006

Identification of ciliary and ciliopathy genes in Caenorhabditis elegans through comparative genomics.

BACKGROUND: The recent availability of genome sequences of multiple related Caenorhabditis species has made it possible to identify, using comparative genomics, similarly transcribed genes in Caenorhabditis elegans and its sister species. Taking this approach, we have identified numerous novel ciliary genes in C. elegans, some of which may be orthologs of unidentified human ciliopathy genes. RESULTS: By screening for genes possessing canonical X-box sequences in promoters of three Caenorhabditis species, namely C. elegans, C. briggsae and C. remanei, we identified 93 genes (including known X-box regulated genes) that encode putative components of ciliated neurons in C. elegans and are subject to the same regulatory control. For many of these genes, restricted anatomical expression in ciliated cells was confirmed, and control of transcription by the ciliogenic DAF-19 RFX transcription factor was demonstrated by comparative transcriptional profiling of different tissue types and of daf-19(+) and daf-19(-) animals. Finally, we demonstrate that the dye-filling defect of dyf-5(mn400) animals, which is indicative of compromised exposure of cilia to the environment, is caused by a nonsense mutation in the serine/threonine protein kinase gene M04C9.5. CONCLUSION: Our comparative genomics-based predictions may be useful for identifying genes involved in human ciliopathies, including Bardet-Biedl Syndrome (BBS), since the C. elegans orthologs of known human BBS genes contain X-box motifs and are required for normal dye filling in C. elegans ciliated neurons.

Animals↗

PubMed2006

Do geriatricians stay in geriatrics?.

To evaluate whether formally trained geriatricians remain in the field of Geriatrics, and to determine their job satisfaction and perceived quality of life, we surveyed the 107 fellows trained over the last 25 years in one accredited geriatric program. Of the 88 physicians who consented to participate, 75% devoted at least half of their practice to the care of the elderly. On an academic level, 89.5% had, or planned to pursue, recertification in geriatric medicine. Ninety-five percent of these geriatricians felt that the impact of a formal geriatric fellowship was positive on their medical career and satisfaction index. Sixty-four percent had yearly incomes between $100 and $200k, and 25.6% had income greater than $200k. Eighty-seven percent would recommend pursuing geriatric fellowship training. We need to further explore how recruitment process and job opportunities are presented to potential geriatric fellows.

Adult↗

PubMed2004

A set of BAC clones spanning the human genome.

Using the human bacterial artificial chromosome (BAC) fingerprint-based physical map, genome sequence assembly and BAC end sequences, we have generated a fingerprint-validated set of 32 855 BAC clones spanning the human genome. The clone set provides coverage for at least 98% of the human fingerprint map, 99% of the current assembled sequence and has an effective resolving power of 79 kb. We have made the clone set publicly available, anticipating that it will generally facilitate FISH or array-CGH-based identification and characterization of chromosomal alterations relevant to disease.

Base Sequence↗

PubMed2004

Predictors of site of death of end-of-life patients: the importance of specificity in advance directives.

Despite the compelling reasons for advance directives and their endorsement by the public and medical professions, little is known about their actual use and impact on site of death. This study was conducted to examine the role of advance directives and other "drivers" of hospitalization of the long-term care end-of-life patient. The medical records of 100 deceased consecutive nursing home residents, stratified by site of death (skilled nursing facility or acute care hospital), were reviewed by a team of geriatric researchers to obtain patient information in the following domains: sociodemographic, advance directives, transfer and death information, patient diagnoses at admission, discharge, and other time intervals; medication usage and signs and symptoms precipitating death. Severity of illness was assessed using the Cumulative Illness Rating Scale-G (CIRS-G). In testing for differences between patients by site of death, sociodemographic variables (gender, age, race, payer at discharge, cognitive capacity) did not significantly differ between the two groups of patients. Strong similarities between the groups were also found in terms of severity of illness and medication usage. Significantly higher proportions of patients dying in the nursing home had specific advance directives (do not resuscitate, do not intubate, do not artificially feed, do not hydrate, and do not hospitalize), as opposed to those dying in the hospital. The findings of this study demonstrate the impact of the explicit advance directive on the decision to transfer the patient to the acute care setting at the end of life.

Advance Directives↗

PubMed2004

Integrated and sequence-ordered BAC- and YAC-based physical maps for the rat genome.

As part of the effort to sequence the genome of Rattus norvegicus, we constructed a physical map comprised of fingerprinted bacterial artificial chromosome (BAC) clones from the CHORI-230 BAC library. These BAC clones provide approximately 13-fold redundant coverage of the genome and have been assembled into 376 fingerprint contigs. A yeast artificial chromosome (YAC) map was also constructed and aligned with the BAC map via fingerprinted BAC and P1 artificial chromosome clones (PACs) sharing interspersed repetitive sequence markers with the YAC-based physical map. We have annotated 95% of the fingerprint map clones in contigs with coordinates on the version 3.1 rat genome sequence assembly, using BAC-end sequences and in silico mapping methods. These coordinates have allowed anchoring 358 of the 376 fingerprint map contigs onto the sequence assembly. Of these, 324 contigs are anchored to rat genome sequences localized to chromosomes, and 34 contigs are anchored to unlocalized portions of the rat sequence assembly. The remaining 18 contigs, containing 54 clones, still require placement. The fingerprint map is a high-resolution integrative data resource that provides genome-ordered associations among BAC, YAC, and PAC clones and the assembled sequence of the rat genome.

Animals↗

PubMed2002

A physical map of the mouse genome.

A physical map of a genome is an essential guide for navigation, allowing the location of any gene or other landmark in the chromosomal DNA. We have constructed a physical map of the mouse genome that contains 296 contigs of overlapping bacterial clones and 16,992 unique markers. The mouse contigs were aligned to the human genome sequence on the basis of 51,486 homology matches, thus enabling use of the conserved synteny (correspondence between chromosome blocks) of the two genomes to accelerate construction of the mouse map. The map provides a framework for assembly of whole-genome shotgun sequence data, and a tile path of clones for generation of the reference sequence. Definition of the human-mouse alignment at this level of resolution enables identification of a mouse clone that corresponds to almost any position in the human genome. The human sequence may be used to facilitate construction of other mammalian genome maps using the same strategy.

Animals↗