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Biomedical subjects

R P Ketterling

Publications and source records attributed to R P Ketterling.

At least 19 recordsLinked to original sources
PubMed2006

Novel FISH probes designed to detect IGK-MYC and IGL-MYC rearrangements in B-cell lineage malignancy identify a new breakpoint cluster region designated BVR2.

Detection of translocations involving MYC at 8q24.1 in B-cell lineage malignancies (BCL) is important for diagnostic and prognostic purposes. However, routine detection of MYC translocations is often hampered by the wide variation in breakpoint location within the MYC region, particularly when a gene other than IGH, such as IGK or IGL, is involved. To address this issue, we developed and validated four fluorescence in situ hybridization (FISH) probes: two break apart probes to detect IGK and IGL translocations, and two dual-color, dual-fusion FISH (D-FISH) probes to detect IGK-MYC and IGL-MYC. MYC rearrangements (four IGK-MYC, 12 IGL-MYC and four unknown partner gene-MYC) were correctly identified in 20 of 20 archival BCL specimens known to have MYC rearrangements not involving IGH. Seven specimens, all of which lacked MYC rearrangements using a commercial IGH/MYC D-FISH probe, were found to have 8q24 breakpoints within a cluster region >350-645 kb 3' from MYC, provisionally designated as Burkitt variant rearrangement region 2 (BVR2). FISH is a useful ancillary tool in identifying MYC rearrangements. In light of the discovery of the distally located BVR2 breakpoint cluster region, it is important to use MYC FISH probes that cover a breakpoint region at least 1.0 Mb 3' of MYC.

B-Lymphocytes↗
PubMed2006

FIP1L1-PDGFRA in eosinophilic disorders: prevalence in routine clinical practice, long-term experience with imatinib therapy, and a critical review of the literature.

We previously studied clinico-pathologic features of 89 consecutive adult patients with moderate-to-severe eosinophilia, and reported a FIP1L1-PDGFRA prevalence of 12%. In that series, all 11 FIP1L1-PDGFRA+ patients receiving imatinib achieved a complete response. We now extend our observations through a study of 741 unselected patients with eosinophilia for FIP1L1-PDGFRA, and present longer term follow up data for the imatinib-treated cohort. We also include data for three previously unreported FIP1L1-PDGFRA+ patients. Among the 741 requests, only 21 (3%) were found to carry the FIP1L1-PDGFRA mutation. While all 14 FIP1L1-PDGFRA+ patients receiving imatinib achieved a complete response, the 4 patients who attempted to discontinue imatinib all relapsed. We also find that it is possible to maintain patients in clinical remission with an empirically derived schedule of low-dose (50-100 mg), intermittent (once daily to once weekly) imatinib. Lastly, we present a comprehensive review of the literature pertaining to FIP1L1-PDGFRA in order to address several key aspects of this mutation from a clinical standpoint.

Adult↗
PubMed2006

Connective tissue dysplasia in five new patients with NF1 microdeletions: further expansion of phenotype and review of the literature.

Approximately 5% of patients with neurofibromatosis type 1 (NF1) have deletions of the entire NF1 gene. The phenotype usually includes early onset, large number of neurofibromas, presence of congenital anomalies, cognitive deficiency, and variable dysmorphic features and growth abnormalities. Connective tissue abnormalities are not generally recognised as a part of NF1 microdeletion syndrome, but mitral valve prolapse, joint laxity, and/or soft skin on the palms have been reported in a few patients. We describe clinical findings in six newly diagnosed patients with NF1 microdeletions, five of whom presented with connective tissue abnormalities. A literature review of the clinical findings associated with NF1 microdeletion was also performed. Our report confirms that connective tissue dysplasia is common in patients with NF1 microdeletions. Given the potential for associated cardiac manifestation, screening by echocardiogram may be warranted. Despite the large number (>150) of patients with known NF1 microdeletions, the clinical phenotype remains incompletely defined. Additional reports of patients with NF1 microdeletions, including comprehensive clinical and molecular information, are needed to elucidate possible genotype-phenotype correlation.

Adolescent↗
PubMed2005

Development of a D-FISH method to detect DEK/CAN fusion resulting from t(6;9)(p23;q34) in patients with acute myelogenous leukemia.

The t(6;9)(p23;q34)-DEK/CAN fusion occurs with an incidence of 1-5% in adult patients with acute myelogenous leukemia (AML) and tends to have an unfavorable prognosis at diagnosis. Due to the subtle appearance of this chromosome rearrangement, both initial detection and minimal residual disease (MRD) tracking by conventional karyotyping can be difficult. Unfortunately, no commercial or previously published fluorescence in situ hybridization (FISH) strategies exist for this recurrent anomaly. We have developed a highly sensitive assay using dual-color, double-fusion FISH (D-FISH), which can be used both for initial detection and MRD monitoring. We analyzed archived bone marrow samples from 15 patients with a previously identified t(6;9)(p23;q34) and 10 corresponding post-treatment samples. The results demonstrate that our D-FISH method effectively identified all abnormal samples, including a low-level MRD sample that was considered to be normal by conventional cytogenetic analysis. Normal value ranges were established from 30 negative controls to be < 0.6% when 500 interphase nuclei were analyzed. The development of this sensitive D-FISH strategy for the detection of the t(6;9)(p23;q34) adds to the AML FISH testing repertoire, and is effective in the detection of low-level disease in post-treatment samples in these patients.

Chromosomes, Human, Pair 6↗
PubMed2000

Inherited interstitial deletion of chromosomes 5p and 16q without apparent phenotypic effect: further confirmation.

We describe two families in which an inherited interstitial deletion is present without apparent associated phenotypic abnormalities. The first deletion was discovered in a 19-year-old male with a previously diagnosed peroxisomal disorder. High-resolution chromosome analysis was interpreted as 46,XY,del(5)(p14.1p14.3). The patient's phenotypically normal mother had the same interstitial deletion. Chromosome 5p14 deletion has been reported in a three-generation family without phenotypic anomalies. We hypothesize that the affected son's phenotype may be coincidental or represent unmasking of an autosomal recessive peroxisomal disorder in the deleted region. The second interstitial deletion was detected by amniocentesis for advanced maternal age. High-resolution chromosome analysis was interpreted as 46,XX,del(16)(q13q22). The same deletion was found in the healthy mother and a normal brother. The pregnancy was carried to term and resulted in the birth of a normal girl. We report these cases as further evidence that rare, unbalanced deletion of specific chromosomal regions may result in no phenotypic effect. Consequences may result from expression of an autosomal recessive disorder on the homologous chromosome. Identification of such deletions is especially important for prenatal diagnosis and genetic counselling.

Adult↗
PubMed1999

Reported in vivo splice-site mutations in the factor IX gene: severity of splicing defects and a hypothesis for predicting deleterious splice donor mutations.

Small consensus sequences have been defined for RNA splicing, but questions about splicing in humans remain unanswered. Analysis of germline mutations in the factor IX gene offers a highly advantageous system for studying the mutational process in humans. In a sample of 860 families with hemophilia B, 9% of independent mutations are likely to disrupt splicing as their primary mode of action. This includes 26 splicing mutations reported herein. When combined with the factor IX splice mutations reported by others, at least 104 independent mutations have been observed, 80 of which are single base substitutions within the splice donor and splice acceptor consensus sequences. After analysis of these mutations, the following inferences emerge: (1) the susceptibility of a splice donor sequence to deleterious mutation depends on the degree of similarity with the donor consensus sequence, suggesting a simple "5-6 hypothesis" for predicting deleterious vs. neutral mutations; (2) the great majority of mutations that disrupt the splice donor or splice acceptor sequences result in at least a 100-fold decrement in factor IX coagulant activity, indicating that the mutations at these sites generally function as an on/off switch; (3) mutations that create cryptic splice junctions or that shorten but do not interrupt the polypyrimidine tract in the splice acceptor sequence can reduce splicing by a variable amount; and (4) there are thousands of potential donor-acceptor consensus sequence combinations in the 38-kb factor IX gene region apparently not reduced by evolutionary selective pressure, presenting an apparent paradox; i.e., mutations in the donor and acceptor consensus sequences at intron/exon splice junctions can dramatically alter normal splicing, yet, appropriately spaced, good matches to the consensus sequences do not predispose to significant amounts of alternative splicing.

Computer Simulation↗
PubMed1999

Germline origins in the human F9 gene: frequent G:C-->A:T mosaicism and increased mutations with advanced maternal age.

The factor IX gene (F9) is an advantageous system for analyzing recent spontaneous germline mutation in humans. Herein, the male:female ratio of mutation ("r") in F9 have been estimated by Bayesian analysis from 59 germline origin families. The overall "r" in F9 was estimated at 3.75. The "r"s varied with the type of mutation. The "r"s ranged from 6.65 and 6.10 for transitions at CpG and A:T to G:C transitions at non-CpG dinucleotides, respectively, to 0.57 and 0.42 for microdeletions/microinsertions and large deletions (>1 kb), respectively. The "r" for the two subtypes of non-CpG transitions differed (6.10 for A:T to G:C vs 0.80 for G:C to A:T). Somatic mosaicism was detected in 11% of the 45 origin individuals for whom the causative mutation was visualized directly by genomic sequencing of leukocyte DNA (estimated sensitivity of approximately one part in 20). Four of the five defined somatic mosaics had G:C to A:T transitions at non-CpG dinucleotides, hinting that this mutation subtype may occur commonly early in embryogenesis. The age at conception was analyzed for 41 US Caucasian families in which the age of the origin parent and the year of conception for the first carrier/hemophiliac were available. No evidence for a paternal age effect was seen. However, an advanced maternal age effect was observed (P=0.03) and was particularly prominent for transversions (average of the 79th percentile when maternal age was normalized for the year of conception). This suggests that an increased maternal age results in a higher rate of transmitted mutation, whereas the increased number of mitotic replications associated with advanced paternal age has little, if any, effect on the rate of transmitted mutation.

Adolescent↗
PubMed1999

Haemophilia B Brandenberg-type promoter mutation.

We report the second confirmed case of the haemophilia B 'Brandenberg' phenotype. At the time of testing, patient HB530 was a 17-year-old post-puberty male with a persistent, clinically severe bleeding disorder and markedly reduced plasma procoagulant factor IX activity (< 1%). Sequencing studies revealed a G-->A transition at bp - 26 within the promoter region of the factor IX gene. This case report confirms the observation that not all patients with promoter mutations improve after puberty and supports the hypothesis that bp - 26 is a critical binding site within the factor IX gene promoter region for both constitutive as well as androgen-inducible transcription factors.

Adolescent↗
PubMed1998

Germline mutations in Peruvian patients with hemophilia B: pattern of mutation in AmerIndians is similar to the putative endogenous germline pattern.

Exogenous (e.g., environmental) mutagens produce characteristic patterns of mutation. In contrast, endogenous mutation processes likely are associated with an invariant pattern of mutation. Analysis of factor IX gene mutations among large samples of hemophilia B patients from multiple, widely divergent geographic and ethnic populations reveals a remarkably constant mutational pattern, suggesting that the primary germline mutational process results from endogenous processes rather than environmental mutagens. To test this hypothesis further, we have initiated a study of hemophilia B patients from Peru because relatively large populations of AmerIndians can be found with low admixtures of other races. To determine if the factor IX (FIX) germline mutational pattern in AmerIndians differs from the common and putative endogenous pattern, FIX gene mutations were characterized in an initial sample of 10 AmerIndian Peruvian patients with hemophilia B. A minimum of 2.2 kb of the FIX gene was examined by PCR and direct sequencing of all eight exons, the splice junctions, and the promoter region. The pattern of germline mutation in AmerIndians was similar to the pattern of FIX germline mutations from larger U. S. Caucasian or Mexican Hispanic samples (P=0.55 and 0.63, respectively). The similar pattern in this initial sample of the Peru AmerIndian population provides additional support for the inference that the FIX germline mutational pattern results from predominantly endogenous processes rather than exogenous mutagens.

Factor IX↗
PubMed1996

Absence of somatic mosaicism in 17 families with hemophilia B: an analysis with a sensitivity 10- to 1000-fold greater than that of sequencing gels.

Most estimates of germ-line mosaicism have been derived from families in which there has been transmission of a mutated allele to two or more children by an unaffected individual. Previously, analyses for somatic mosaicism detected five such individuals by PCR-based sequencing and haplotype analysis at a sensitivity of approximately 1 mutant per 10 wild-type alleles. To determine whether mutations that occur later in embryogenesis also give rise to somatic mosaicism, we analyzed leukocyte DNA from 17 individuals in whom a mutation in the factor IX gene was known to have originated. Methods capable of detecting 1 mutant allele in 100-10,000 were utilized, and no further examples of somatic mosaicism were detected. If confirmed by future studies, the paucity of somatic mosaicism with mutant:wild-type allele frequencies ranging from 1:10 to 1:1000 (relative to the 11% of somatic mosaicism detected with mutant:wild-type allele frequencies of 1:1 to 1:10) may reflect a higher mutation rate and/or germ-line lineage allocation very early in embryogenesis.

Alleles↗
PubMed1996

The factor IX gene as a model for analysis of human germline mutations: an update.

The variation generated by germline mutation is essential for evolution, but individuals pay a steep price in the form of Mendelian disease and genetic predisposition to complex disease. Indeed, the health of a species is determined ultimately by the rate of germline mutation. Analysis of the factor IX gene in patients with hemophilia B has provided insights into the human germline mutational process. Herein, seven topics will be reviewed with emphasis on recent advances: (i) proposed mechanisms of deletions, inversions, and insertions; (ii) discordant sex ratios of mutation and associated age effects; (iii) somatic mosaicism; (iv) founder effects; (v) mutation rates; (vi) the factor IX gene as a germline mutagen test; and (vii) cancer as a possible mechanism for maintaining a constant rate of germline mutation.

Age Factors↗
PubMed1995

Factor VIII gene inversions in severe hemophilia A: results of an international consortium study.

Twenty-two molecular diagnostic laboratories from 14 countries participated in a consortium study to estimate the impact of Factor VIII gene inversions in severe hemophilia A. A total of 2,093 patients with severe hemophilia A were studied; of those, 740 (35%) had a type 1 (distal) factor VIII inversion, and 140 (7%) showed a type 2 (proximal) inversion. In 25 cases, the molecular analysis showed additional abnormal or polymorphic patterns. Ninety-eight percent of 532 mothers of patients with inversions were carriers of the abnormal factor VIII gene; when only mothers of nonfamilial cases were studied, 9 de novo inversions in maternal germ cells were observed among 225 cases (approximately 1 de novo maternal origin of the inversion in 25 mothers of sporadic cases). When the maternal grandparental origin was examined, the inversions occurred de novo in male germ cells in 69 cases and female germ cells in 1 case. The presence of factor VIII inversions is not a major predisposing factor for the development of factor VIII inhibitors; however, slightly more patients with severe hemophilia A and factor VIII inversions develop inhibitors (130 of 642 [20%]) than patients with severe hemophilia A without inversions (131 of 821 [16%]).

Blotting, Southern↗
PubMed1995

Molecular epidemiology of factor IX germline mutations in Mexican Hispanics: pattern of mutation and potential founder effects.

Germline mutations in patients with hemophilia B generally have arisen within the past 150 years. Evidence suggests that these germline mutations generally result from endogenous processes. However, a unique pattern would be expected if a population were exposed to a physiologically important germline mutagen since mutagens generally produce characteristic patterns, or "fingerprints", of mutation. To determine the pattern of mutation in Mexican Hispanics, the regions of likely functional significance in the factor IX gene were screened by dideoxy fingerprinting (ddF) in 31 families with hemophilia B. Mutations were found in 30 of these families. Haplotype analysis was performed on individuals with identical mutations to help distinguish independent, recurrent mutations from founder effects. Analysis of these 30 mutations, along with 7 mutations reported previously in Mexican Hispanic families, reveals a pattern of independent mutation that is similar to the pattern of mutation observed in 127 U.S. Caucasian families (p = 0.89). These results may reflect either an underlying pattern of germline mutation due to endogenous processes or the presence of an ubiquitous mutagen. Further analyses of the recurrent mutations revealed that two mutations, T296M and R248Q, accounted for 19% of the mutations found in the Mexicans. Haplotype data suggest that the multiple occurrences of T296M and R248Q are associated with founder effects and that screening for these mutations may allow rapid mutation detection and carrier diagnosis in a significant minority of Mexican families with hemophilia B, These two mutations also are associated with founder effects in the U.S, Caucasian population. However, the haplotypes are different in these two populations, indicating independent origins. The occurrence of identical founder mutations in distinct populations provides evidence for the previous hypothesis that the number of different mutations giving rise to mild or borderline mild/moderate hemophilia B is small compared to deleterious mutations causing more severe disease.

Factor IX↗
PubMed1994

How precisely can data from transgenic mouse mutation-detection systems be extrapolated to humans?: lesions from the human factor IX gene.

Transgenic mutation-detection systems have been pioneered in mice, but the approach is applicable to any species in which transgenic animals can be generated. The observed mutations seen in mutation-detection systems are influenced by the underlying pattern of mutation, i.e., the mutational pattern that occurs in wild-type organisms in endogenous segments of DNA that are not under selective pressure. Unfortunately, the biology of most genes and assays markedly skew the underlying pattern of mutation. Herein, we raise multiple issues that must be addressed in order to estimate the underlying pattern of spontaneous mutation from transgenic mouse mutation-detection systems. If these issues can be addressed, the underlying pattern of spontaneous mutation can then be deduced for multiple cell types and for transgenes integrated into different parts of the genome. Even though transgenic methodology cannot be applied directly to humans, it is likely that comparable data on the underlying pattern of spontaneous mutation will be available in humans. Such data are currently available for germline mutations in the factor IX gene. These data are reviewed because of their relevance to two of the multiple issues that must be addressed in transgenic mouse mutation-detection systems: (1) How can the underlying pattern of mutation be deduced from the observed pattern? and (2) How similar are the underlying patterns of mutation in humans and in mice? The analysis of recent germ-line mutation in the factor IX gene yield estimates of the mutation rates per base pair per generation. In brief, the mutation rates vary from 0.037 x 10(-10) for deletions (> 20 bp) to 360 x 10(-10) for transitions at the dinucleotide CpG. If these mutation rates are extrapolated to the entire genome, the aggregate mutation rate is estimated to be 36 x 10(-10). This implies that the diploid genome of each person contains about 21 de novo mutations. In the future, the underlying pattern of spontaneous mutation will be deduced for multiple human genes and these will serve as benchmarks to assess the similarity of the mutational process in humans and in mice.

Animals↗
PubMed1994

"Cryptic" dinucleotide polymorphism in the 3' region of the factor IX gene shows substantial variation among different populations.

Long tandem dinucleotide repeats composed of alternating purines and pyrimidines [RY(i)] are abundant and highly polymorphic. "Simple" RY(i) are predominantly composed of one tandem repeat of a dinucleotide sequence. In contrast, "cryptic" RY(i) [cRY(i)] are composed of multiple short dinucleotide repeats. Herein, we describe the racial distribution of alleles for a polymorphic cRY(i) in the factor IX gene. Allele I is absent in Asians, whereas allele III is rare or absent in Caucasians or blacks. A polymorphic cRY(i) analyzed previously shows even more dramatic variation among racial groups, hinting that a battery of cRY(i) might have utility in assessing the racial origin of a DNA sample.

Alleles↗