Detection of RB1 deletions by fluorescence in situ hybridization in malignant hematologic disorders.

We evaluated the usefulness of fluorescence in situ hybridization (FISH) using different-colored commercial RB1 and 13qter DNA probes to identify RB1 deletions in interphase nuclei of bone marrow from 24 patients with agnogenic myeloid metaplasia (AMM), 20 patients with multiple myeloma (MM), 21 patients with other hematologic malignancies, and 25 normal bone marrow transplant (BMT) donors. Based on the 25 normal BMT donors, the upper boundary for the normal percentage of nuclei with one RB1 signal was 6.5%. Based on eight specimens known to have a deletion of 13q14 by cytogenetic studies, the lower limit of abnormal for the percentage of nuclei with one RB1 signal was 12.5%. More than 12.5% of nuclei had a single RB1 signal in 7/24 (29%) patients with AMM and 3/20 (15%) patients with MM. None of the 21 patients with hematologic malignancies other than AMM or MM had more than 12.5% nuclei with loss of RB1. The results of this study suggest that FISH with RB1 probes is useful to detect loss of RB1 in interphase nuclei from patients with hematologic disorders who have chromosome abnormalities involving 13q14. Thus, FISH with probes for RB1 is efficacious to investigate the pathogenesis of RB1 in malignant neoplasms and is a useful adjunct to conventional cytogenetic studies in clinical practice when abnormalities of 13q14 are involved.

Utility of the cervical spine radiograph in pediatric trauma.

To determine the utility of the routine cervical spine radiograph, we reviewed all cervical spine radiographs obtained in pediatric trauma patients over a 2 1/2-year period at the Childrens Hospital of Los Angeles. Records of patients admitted with a documented cervical spine injury over a 20-year period were also reviewed. One hundred eighty-seven children had at least one cervical spine radiograph. Forty-six patients (25 percent) required at least one repeat study in an attempt to see all 7 vertebrae. Thirty-eight children (20 percent) had a second radiograph and 8 patients had a third study, all of which showed no injury. There was only one fracture seen during the 2 1/2-year time period. Of the 16 children admitted over the 20-year period, only 3 sustained an injury below the fourth cervical vertebra (C4), and all were over 8 years of age. All patients with cervical spine injury were either comatose or had symptoms referable to the neck. We conclude that the routine cervical spine radiograph in pediatric trauma is a very low-yield test.

Detection of enteroviruses using subgenomic probes of Coxsackie virus B4 by hybridization.

The objective of this research was to develop group- and type-specific probes for the detection of enteroviruses. Coxsackie virus B4 RNA was cloned, and a series of subgenomic clones were generated. Six of these clones, containing sequences from the 3' end or the 5' end of the genome, were tested for their ability to detect these viruses in a small number of infected cells employing nucleic acid hybridization technique and total cytoplasmic RNA from a panel of 11 serotypes of enteroviruses. The RNA from cells infected with Coxsackie B viruses gave characteristic and positive hybridization signals. Coxsackie B-specific probes and a control Echo 9 probe detected Coxsackie A9 and Echo 3 weakly. As little as 0.5 microgram of the RNA--which contained 10-20 ng of poly(A)-containing, virus-specific, hybridizable RNA--was sufficient to successfully conduct the assay, suggesting high sensitivity of these probes. Probes that are 3' end-specific appear to be group specific, while those that are 5' end-specific appear to be type specific among the serotypes tested.

The organization and evolution of cloned globin genes.

The globin genes represent a complex set of sequences that are expressed in a coordinate fashion during the development of red blood cells. while this complex family of genes may consist of as many as ten to fourteen members [34], three of these genes have now been cloned and their entire nucleotide sequence determined. As was initially observed in the case of beta globin major gene, all are encoded in three distinct coding blocks separated by two intervening sequences of DNA. Their intervening sequences of DNA are preserved, with respect to location, but are widely divergent, with respect to size and sequence. The divided information in each gene is edited and spliced together at the level of its initial RNA transcript which is complementary to the entire gene sequence including its intervening sequences. Structural correlation analyses have allowed us to identify sites in all three genes that might be responsible for the initiation of transcription, RNA splicing, and poly A addition. The function of these sites has been tested by cloning these genes in an animal virus vector SV40. Such animal virus hybrids have been used to infect tissue culture cells and have directed the synthesis of both alpha and beta mouse globin in cells of monkey origin. These studies indicate that such signals operate across species barriers and further indicate that the animal virus vector system will be useful in elucidating their function.

A mouse globin gene promoter is functional in SV40.

We have constructed two SV40 recombinants carrying a complete mouse alpha-globin gene with its presumptive promoter region. In one recombinant the globin gene can be transcribed either from its own promoter or from the adjacent viral late region promoter. In the other efficient globin expression should depend only upon the promoter carried by the chromosomal globin gene. We show that both viruses direct the synthesis of functional globin mRNA in infected monkey kidney cells and that this mRNA has a 5' terminus indistinguishable from that of authentic globin mRNA. These results suggest that the cloned globin gene contains a functional promoter that is accurately recognized in monkey kidney cells.

Cytoplasmic location of undermethylated messenger RNA in Novikoff cells.

Novikoff cells in culture were labeled with L-[methyl-3H]methionine and [U-14C]uridine in the presence of (a) TubHcy2, (b) AdoHcy, (c) homocysteine, (d) tubercidin, or (e) without any additions. Only in cultures labeled in the presence of TubHcy were undermethylated cap structures observed to represent a significant portion of [3H]methyl radioactivity. Novikoff cells in culture were then simultaneously labeled with L-[methyl-3H]methionine and [32P]orthophosphate in the presence or absence of TubHcy. Total cytoplasmic, polysomal and monosomal poly(A)-containing RNAs were analyzed. Both monosomal and polysomal mRNA fractions from TubHcy-treated cells contain partially methylated cap structures, suggesting that 2'-O-methylation of the nucleoside adjacent to the pyrophosphate linkage in caps is not required for transport, ribosomal binding or translation. Comparison of nuclear and cytoplasmic cap structures from normal and inhibited cultures indicate that an altered mRNA population is generated in the presence of TubHcy.

In vivo inhibition of Novikoff cytoplasmic messenger RNA methylation by S-tubercidinylhomocysteine.

The analogue S-tubercidinylhomocysteine (STH) has been used to study the methylation of mRNA in vivo. Partial inhibition of cytoplasmic poly(A)-RNA methylation was observed using a level of inhibitor which still permitted cell growth. Characterization of the partially methylated mRNA indicated the presence of cap structures lacking 2'-O-methylnucleosides, m7GpppN', which are normally not found in mammalian mRNA. Inhibition of additional methylated sites in mRNA at the second 2'-O-methynucleoside, and at internal N6-methyladenosine was also observed Methylation of 7-methylguanosine was not affected under the conditions used in these experiments. The methylnucleoside composition of cap structures differed in STH-inhibited and uninhibited cells. These results indicate that a completely methylated cap is not required for transport of mRNA into the cytoplasm. Furthermore, it may now be possible to assess in vivo the sequential nature of mRNA methylation and its potential role in mRNA processing.

Kinetics of Novikoff cytoplasmic messenger RNA methylation.

Methylation patterns of Novikoff cytoplasmic mRNA were determined as a function of labeling time with L-[methyl-3H]methionine. The 5'-terminal m7G could be released from whole mRNA by treatment with nucleotide pyrophosphatase. Subsequent alkaline phosphatase treatment of this mRNA, followed by KOH digestion, yielded N'mpNp and N'mpNp from cap 1 (m7GpppN'mpN) and cap 2 (m7GpppN'mpN''mpN), respectively. Our results indicate that the relative amounts of labeled cap structures do change with time and that the amount of internal N6-methyladenosine decreases, relative to 5'-cap structures, as the cytoplasmic mRNAs age and the average size decreases. The formation of cap-2 structures by the addition of second 2'-O-methyl group at position N''m appears to be cytoplasmic event. Thus, after very short labeling times, greater than 80% of the labeled methyl groups in cap 2 are found in this position. These results, along with earlier data obtained on L-cell heterogeneous nuclear RNA methylation, are consistent with a model in which the nucleus is the cellular site of three mRNA methylation events producing 5'-terminal m7G, the first 2'-O-methylnucleoside (N'm) found in cap-1 structures and internal N6-methyladenosine. Subsequently, these nuclear methylations are followed by the cytoplasmic methylation at N''m. Analysis of the methynucleoside composition of cap-1 structures, along with comparable "core" structures (m7GpppN'm) generated from cap-2 by removal of N''m, indicates that at any single labeling time the methylnucleoside composition of a given cap-1 and the cap-2 "core" structure is remarkably similar. On the other hand, comparisons of the methylnucleoside composition of the cap structures at different labeling times indicate an increase in Cm in the first 2'-O-methylnucleoside (N'm) with time.