Morphologic and cytogenetic variables affect the flow cytometric recovery of plasma cell myeloma cells in bone marrow aspirates.

INTRODUCTION: It is widely recognized that plasma cells (PCs) are under-represented in flow cytometry (FC) studies, but the causes of this phenomenon are poorly understood. We sought to study potential variables that affect PC recovery by flow cytometry (FC) in the analysis of plasma cell myeloma (PCM). METHODS: We retrospectively performed PC differential counts and morphologic assessment on PCM peripheral blood (PB) smears, bone marrow (BM) aspirate smears and posterythrocyte lysis cytospins. PCs were enumerated by FC, excluding erythroid events/debris, and were defined as CD38(bright+), CD45(dim to negative) events. PC recovery was calculated as follows: cytospin/aspirate, FC/aspirate, and FC/cytospin. RESULTS: Sixty-four BM analyses from 42 patients showed a mean aspirate PC% of 32.9 ± 23.2%. The mean PC% decreased in both the cytospin (10.9%) and by FC (8.2%). The difference between PC% in the cytospin and by FC was statistically significant (P < 0.03). Mature PC morphology and lower aspirate PC% had poorer recovery (P < 0.05) but higher-risk cytogenetics (deletions of 13q and TP53) was associated with increased PC recovery. Immunophenotype, heavy chain type, and treatment did not affect PC recovery. PB specimens had superior recovery compared with BM samples. CONCLUSIONS: Similar to prior reports, the greatest loss of PC in BM evaluation occurs between the aspirate and postlysis specimens; however, a small amount occurs from further processing. Additional morphologic and cytogenetic factors also appear to influence recovery in addition to overall PC%.

A multicenter investigation with interphase fluorescence in situ hybridization using X- and Y-chromosome probes.

Twenty-six laboratories used X and Y chromosome probes and the same procedures to process and examine 15,600 metaphases and 49,400 interphases from Phaseolus vulgaris-leucoagglutinin (PHA)-stimulated lymphocytes. In Part I, each laboratory scored 50 metaphases and 200 interphases from a normal male and a normal female from its own practice. In Part II, each laboratory scored 50 metaphases and 200 interphases on slides prepared by a central laboratory from a normal male and a normal female and three mixtures of cells from the male and female. In Part III, each laboratory scored 50 metaphases (in samples of 5, 10, 15, and 20) and 100 interphases (in samples of 5, 10, 15, 20, and 50) on new, coded slides of the same specimens used in Part II. Metaphases from male specimens were scored as 98-99% XY with no XX cells, and 97-98% of interphases were scored as XY with 0.04% XX cells. Metaphases from female specimens were scored as 96-97% XX with 0.03% XY cells, and 94-96% of interphases were scored as XX with 0.05% XY cells. Considering the data as a model for any probe used with fluorescence in situ hybridization (FISH), a statistical approach assessing the impact of analytical sensitivity on the numbers of observations required to assay for potential mosaicisms and chimerisms is discussed. The workload associated with processing slides and scoring 50 metaphases and 200 interphases using FISH averaged 27.1 and 28.6 minutes, respectively. This study indicates that multiple laboratories can test/develop guidelines for the rapid, efficacious, and cost-effective integration of FISH into clinical service.

The human PECAM1 gene maps to 17q23.

We have determined the chromosomal and regional location of the gene encoding PECAM-1 (termed PECAM1 by GBD nomenclature) using a polymerase chain reaction (PCR)-based analysis of somatic cell hybrids. Analysis of a somatic cell hybrid chromosome panel established that the PECAM1 gene is on chromosome 17. Interestingly, several adhesion molecules expressed on platelets and endothelium also localize to chromosome 17: the GP1BA locus (glycoprotein (GP) Ibalpha) has been provisionally mapped to the region 17p12-pter, the ITGA2B (GPIIb) and the ITGB3 (GPIIIa) loci have been confirmed to the region 17q21.32; and the ICAM2 locus has been provisionally mapped to the region 17q23-q25. To determine if the PECAM1 locus colocalizes with any of the loci for these adhesion molecules, PCR-based analysis of a regional mapping panel for human chromosome 17 was conducted. We found that the PECAM1 locus is on the long arm of chromosome 17, in the region q23-qter. To confirm this observation and obtain a more precise localization of the PECAM1 locus, fluorescence in situ hybridization was conducted. Together our data allowed assignment of the PECAM1 locus to the region 17q23.

Molecular characterization of human and bovine rod photoreceptor cGMP phosphodiesterase alpha-subunit and chromosomal localization of the human gene.

Defects in proteins that function in photoreceptor signal transduction are prime suspects as causes of some human hereditary retinal degenerations. We have characterized cDNA clones encoding the alpha-subunit of human and bovine rod cell cGMP phosphodiesterase a key phototransduction enzyme. Clones from both species contain an open reading frame capable of coding for an approximately 100-kDa polypeptide of 859 amino acids, 94% of which are identical. Two or more transcripts were detected in both human and bovine retinal poly(A)+ RNA preparations, although the human transcripts ranging from 5.3 to 4.9 kb are significantly larger than the two bovine transcripts of 4.6 and 4.0 kb. The bovine and human genes appear to exist in single copy, with the bovine gene spanning more than 140 kb of genomic DNA. Somatic cell hybrids were used to map the human gene to the long arm of chromosome 5 (5q31.2----q34). Finally, the use of the candidate gene approach in the study of hereditary retinal dystrophies is discussed.

Molecular dissection of a contiguous gene syndrome: frequent submicroscopic deletions, evolutionarily conserved sequences, and a hypomethylated "island" in the Miller-Dieker chromosome region.

The Miller-Dieker syndrome (MDS), composed of characteristic facial abnormalities and a severe neuronal migration disorder affecting the cerebral cortex, is caused by visible or submicroscopic deletions of chromosome band 17p13. Twelve anonymous DNA markers were tested against a panel of somatic cell hybrids containing 17p deletions from seven MDS patients. All patients, including three with normal karyotypes, are deleted for a variable set of 5-12 markers. Two highly polymorphic VNTR (variable number of tandem repeats) probes, YNZ22 and YNH37, are codeleted in all patients tested and make molecular diagnosis for this disorder feasible. By pulsed-field gel electrophoresis, YNZ22 and YNH37 were shown to be within 30 kilobases (kb) of each other. Cosmid clones containing both VNTR sequences were identified, and restriction mapping showed them to be less than 15 kb apart. Three overlapping cosmids spanning greater than 100 kb were completely deleted in all patients, providing a minimum estimate of the size of the MDS critical region. A hypomethylated island and evolutionarily conserved sequences were identified within this 100-kb region, indications of the presence of one or more expressed sequences potentially involved in the pathophysiology of this disorder. The conserved sequences were mapped to mouse chromosome 11 by using mouse-rat somatic cell hybrids, extending the remarkable homology between human chromosome 17 and mouse chromosome 11 by 30 centimorgans, into the 17p telomere region.

Chromosome 17 deletions and p53 gene mutations in colorectal carcinomas.

Previous studies have demonstrated that allelic deletions of the short arm of chromosome 17 occur in over 75% of colorectal carcinomas. Twenty chromosome 17p markers were used to localize the common region of deletion in these tumors to a region contained within bands 17p12 to 17p13.3. This region contains the gene for the transformation-associated protein p53. Southern and Northern blot hybridization experiments provided no evidence for gross alterations of the p53 gene or surrounding sequences. As a more rigorous test of the possibility that p53 was a target of the deletions, the p53 coding regions from two tumors were analyzed; these two tumors, like most colorectal carcinomas, had allelic deletions of chromosome 17p and expressed considerable amounts of p53 messenger RNA from the remaining allele. The remaining p53 allele was mutated in both tumors, with an alanine substituted for valine at codon 143 of one tumor and a histidine substituted for arginine at codon 175 of the second tumor. Both mutations occurred in a highly conserved region of the p53 gene that was previously found to be mutated in murine p53 oncogenes. The data suggest that p53 gene mutations may be involved in colorectal neoplasia, perhaps through inactivation of a tumor suppressor function of the wild-type p53 gene.

Structural analysis of a hepatitis B virus genome integrated into chromosome 17p of a human hepatocellular carcinoma.

Hepatitis B virus (HBV) is clearly a factor in the development of hepatocellular carcinoma, but its mechanism of action remains obscure. One possibility is that the HBV integration event alters the expression of a nearby growth-regulatory cellular gene. A 9-kilobase (kb) DNA fragment containing an HBV insert plus flanking cellular sequences was cloned from a hepatoma specimen from Shanghai, People's Republic of China. Restriction mapping of the insert revealed a large inverted repeat structure consisting of both viral sequences (encompassing all of the core and pre-S regions and portions of the X and S genes) and at least 3 kb of unique cellular sequences. The virus-cell junction mapped 11 nucleotides from the DR1 region, in a position within the HBV X gene and included in the cohesive overlap region. A probe generated from 1.0 kb of the flanking cellular DNA mapped the viral insert to chromosome 17 in the region designated 17p11.2-17p12, which is near the human proto-oncogene p53. Sequence data from a portion of the flanking cellular DNA revealed a stretch of approximately 70 base pairs that showed highly significant homology with a conserved region of a number of functional mammalian DNAs, including the human autonomously replicating sequence 1 (ARS1).

Molecular detection of microscopic and submicroscopic deletions associated with Miller-Dieker syndrome.

Miller-Dieker syndrome (MDS), a disorder manifesting the severe brain malformation lissencephaly ("smooth brain"), is caused, in the majority of cases, by a chromosomal microdeletion of the distal short arm of chromosome 17. Using human chromosome 17-specific DNA probes, we have begun a molecular dissection of the critical region for MDS. To localize cloned DNA sequences to the MDS critical region, a human-rodent somatic cell hybrid panel was constructed which includes hybrids containing the abnormal chromosome 17 from three MDS patients with deletions of various sizes. Three genes (myosin heavy chain 2, tumor antigen p53, and RNA polymerase II) previously mapped to 17p were excluded from the MDS deletion region and therefore are unlikely to play a role in its pathogenesis. In contrast, three highly polymorphic anonymous probes, YNZ22.1 (D17S5), YNH37.3 (D17S28), and 144-D6 (D17S34), were deleted in each of four patients with visible deletions, including one with a ring chromosome 17 that is deleted for a portion of the single telomeric prometaphase subband p13.3. In two MDS patients with normal chromosomes, a combination of somatic cell hybrid, RFLP, and densitometric studies demonstrated deletion for YNZ22.1 and YNH37.3 in the paternally derived 17's of both patients, one of whom is also deleted for 144-D6. The results indicate that MDS can be caused by submicroscopic deletion and raises the possibility that all MDS patients will prove to have deletions at a molecular level. The two probes lie within a critical region of less than 3,000 kb and constitute potential starting points in the isolation of genes implicated in the severe brain maldevelopment in MDS.

Mapping of human methylmalonyl CoA mutase (MUT) locus on chromosome 6.

Methylmalonyl CoA mutase (MCM) catalyzes an essential step in the degradation of several branch-chain amino acids and odd-chain fatty acids. Deficiency of this apoenzyme causes the mut form of methylmalonic acidemia, an often fatal disorder of organic acid metabolism. An MCM cDNA has recently been obtained from human liver cDNA libraries. This clone has been used as a probe to determine the chromosomal location of the MCM gene and MUT locus. Southern blot analysis of DNA from human-hamster somatic-cell hybrid cell lines assigned the locus to region q12-p23 of chromosome 6. In situ hybridization further localized the locus to the region 6p12-21.2. A highly informative RFLP was identified at the MCM gene locus which will be useful for genetic diagnostic and linkage studies.

Human hepatic lipase. Cloned cDNA sequence, restriction fragment length polymorphisms, chromosomal localization, and evolutionary relationships with lipoprotein lipase and pancreatic lipase.

Human hepatic lipase is an important enzyme in high density lipoprotein (HDL) metabolism, being implicated in the conversion of HDL2 to HDL3. Three human hepatic lipase cDNA clones were identified in two lambda gt11 libraries from human liver. The cDNA-derived amino acid sequence predicts a protein of 476 amino acid residues, preceded by a 23-residue signal peptide. Four potential N-glycosylation sites are identified, two of which are conserved in rat hepatic lipase. On alignment with human, mouse, and bovine lipoprotein lipase, the same two sites were also conserved in lipoprotein lipase in all three species. Stringent conservation of the cysteine residues was also evident. Comparative analysis of amino acid sequences shows that hepatic lipase evolves at a rapid rate, 2.07 x 10(-9) substitutions/site/year, about four times that in lipoprotein lipase and half that in pancreatic lipase. Further, hepatic lipase and pancreatic lipase appear to be evolutionarily closer to each other than either of them is to lipoprotein lipase. Southern blot analysis revealed high frequency restriction fragment length polymorphisms of the hepatic lipase gene for the enzymes HindIII and MspI. these polymorphisms will be useful for haplotype and linkage analysis of the hepatic lipase gene. Using cloned human hepatic lipase cDNA as a hybridization probe, we performed Southern blot analysis of a panel of 13 human-rodent somatic cell hybrids. Concordance analysis of the various hybrid clones indicates that the hepatic lipase gene is located on the long arm of human chromosome 15. Analysis of hybrids containing different translocations of chromosome 15 localized the gene to the region 15q15----q22.

Molecular cloning and characterization of a cDNA for human granulocyte colony-stimulating factor (G-CSF) from a glioblastoma multiforme cell line and localization of the G-CSF gene to chromosome band 17q21.

The conditioned media (CM) of the glioblastoma multiforme cell line, U87 MG, contains abundant granulocyte colony-stimulating factor (G-CSF) activity (Tweardy et al., 1987). An oligonucleotide encoding the amino acids -11 to -4 of G-CSF detected a single abundant G-CSF mRNA of 1.6 kilobases (Kb) produced by U87 MG cells. Screening of a U87 MG cDNA library with the oligonucleotide identified cDNA clones of 1.3-1.4 Kb. Sequencing of one clone (pG-CSF6) confirmed that it encoded G-CSF and was derived from G-CSFb mRNA encoding a protein with a three amino acid deletion at positions 36-38. Only a single base substitution was observed at the third position of the codon for leu 152 indicating that G-CSF is highly conserved in cells of widely different origin. Somatic cell hybridization studies and chromosomal in situ hybridization localized the G-CSF gene to the long arm of chromosome 17 in band 17q21, proximal to the 17q breakpoint characteristic of acute promyelocytic leukemia.

Isolation of cDNA clones for the catalytic gamma subunit of mouse muscle phosphorylase kinase: expression of mRNA in normal and mutant Phk mice.

We have isolated and characterized cDNA clones for the gamma subunit of mouse muscle phosphorylase kinase (gamma-Phk). These clones were isolated from a lambda gt11 mouse muscle cDNA library via screening with a synthetic oligonucleotide probe corresponding to a portion of the rabbit gamma-Phk amino acid sequence. The gamma-Phk cDNA clones code for a 387-amino acid protein that shares 93% amino acid sequence identity with the corresponding rabbit amino acid sequence. RNA gel blot analysis reveals that the muscle gamma-Phk probe hybridizes to two mRNA species (2.4 and 1.6 kilobases) in skeletal muscle, cardiac muscle, and brain, but does not hybridize to liver RNA. Phk-deficient I-strain (Phk) mouse muscle contains reduced levels of gamma-Phk mRNA as compared with control mice. Although the Phk defect is an X-linked recessive trait, hybridization to a human-rodent somatic cell hybrid mapping panel shows that the gamma-Phk gene is not located on the X chromosome. Rather, the gamma-Phk cross-hybridizing human restriction fragments map to human chromosomes 7 (multiple) and 11 (single). Reduced gamma-Phk mRNA in I-strain mice, therefore, appears to be a consequence of the Phk-mutant trait and does not stem from a mutant gamma-subunit gene.

Molecular cloning and chromosomal localization of human 4-beta-galactosyltransferase.

A cDNA clone to human 4-beta-galactosyltransferase (EC 2.4.1.38) was isolated from a human liver lambda gt11 expression library by using a monospecific polyclonal antiserum to affinity-purified bovine enzyme. The authenticity of this cDNA clone has been demonstrated by several criteria. Under conditions of chronic treatment with the beta-adrenergic receptor agonist isoproterenol, rat parotid glands show an approximately 10-fold increase in 4-beta-galactosyltransferase activity. The increased enzyme activity was reflected in dot-blot analysis of control and isoproterenol-treated rat parotid RNA by using the human cDNA as probe. Hybrid-selection and in vitro translation identified a protein product with a molecular mass of 47 kDa that was immunoprecipitated with the bovine antiserum. The full-length human cDNA clone was then isolated and the DNA sequence for the NH2-terminal portion of the protein was deduced. Comparison of the NH2-terminal protein sequence from the bovine protein with that of the human cDNA clone confirmed its identity. In addition, the human cDNA clone was used to localize the gene for 4-beta-galactosyltransferase to human chromosome 4 by Southern analysis of a somatic cell hybrid panel.

The anonymous polymorphic DNA clone D1S1, previously mapped to human chromosome 1p36 by in situ hybridization, is from chromosome 3 and is duplicated on chromosome 1.

D1S1, a human anonymous DNA clone originally called lambda Ch4A-H3 or lambda H3, was mapped by two other laboratories to human chromosome 1p36 by in situ hybridization but its localization was not confirmed using a different mapping method. We used a panel of human-hamster somatic cell hybrids to show that there are copies of D1S1 on both chromosomes 1 and 3. The D1S1 clone itself is from chromosome 3, and part of it is duplicated at least twice on chromosome 1. A high frequency HindIII polymorphism detected by D1S1, believed to be at chromosome 1p36 on the basis of the in situ hybridization data, maps instead to chromosome 3. This finding demonstrates the importance of using two mapping methods to verify the localization of a gene or DNA segment, particularly a polymorphic one which itself may be used in mapping studies. It also raises the question of why in situ hybridization detected a duplicated portion of a clone but not the chromosomal origin of the clone itself.

The human apolipoprotein B-100 gene: a highly polymorphic gene that maps to the short arm of chromosome 2.

Using a cloned cDNA of apolipoprotein B-100 as hydridization probe, we have found high frequence polymorphisms in the apoB-100 gene involving sites for the restriction enzymes EcoRI, BamHI, and HindIII. The major EcoRI polymorphisms involved a 17 kb vs 15 kb variant. The incidence of the various phenotypes was estimated. In addition, other complex polymorphisms involving MspI and TaqI sites were also noted. [32P]-labeled apoB-100 cDNA was used as a probe in chromosome mapping studies to detect the human apoB-100 structural gene sequence in human-Chinese hamster and human-mouse cell hybrids. Southern blot analysis of 14 hybrids localized the gene to the short arm of human chromosome 2.