Mutations of the gene encoding the protein kinase A type I-alpha regulatory subunit in patients with the Carney complex.

Carney complex (CNC) is a multiple neoplasia syndrome characterized by spotty skin pigmentation, cardiac and other myxomas, endocrine tumours and psammomatous melanotic schwannomas. CNC is inherited as an autosomal dominant trait and the genes responsible have been mapped to 2p16 and 17q22-24 (refs 6, 7). Because of its similarities to the McCune-Albright syndrome and other features, such as paradoxical responses to endocrine signals, genes implicated in cyclic nucleotide-dependent signalling have been considered candidates for causing CNC (ref. 10). In CNC families mapping to 17q, we detected loss of heterozygosity (LOH) in the vicinity of the gene (PRKAR1A) encoding protein kinase A regulatory subunit 1-alpha (RIalpha), including a polymorphic site within its 5' region. We subsequently identified three unrelated kindreds with an identical mutation in the coding region of PRKAR1A. Analysis of additional cases revealed the same mutation in a sporadic case of CNC, and different mutations in three other families, including one with isolated inherited cardiac myxomas. Analysis of PKA activity in CNC tumours demonstrated a decreased basal activity, but an increase in cAMP-stimulated activity compared with non-CNC tumours. We conclude that germline mutations in PRKAR1A, an apparent tumour-suppressor gene, are responsible for the CNC phenotype in a subset of patients with this disease.

Perivascular cells harboring multiple endocrine neoplasia type 1 alterations are neoplastic cells in angiofibromas.

Although neoplasia is caused by clonal proliferation of cells, the resulting tumors are frequently heterogeneous, being composed of both neoplastic and reactive cells. Therefore, identification of tumors as neoplastic processes is frequently obscured. We studied cutaneous angiofibroma, which is a tumor of unknown etiology. Combined analysis using immunohistochemistry, selective tissue microdissection, fluorescence in situ hybridization, sequencing analysis, and deletion analysis of the multiple endocrine neoplasia type 1 locus succeeded in the identification of a population of genetically altered, neoplastic cells in these tumors. This approach may be valuable in the future in identifying the etiology of other tumors of unknown etiology.

Duplication of the mutant RET allele in trisomy 10 or loss of the wild-type allele in multiple endocrine neoplasia type 2-associated pheochromocytomas.

Inherited mutations of the RET proto-oncogene are tumorigenic in patients with multiple endocrine neoplasia type 2 (MEN 2). However, it is not understood why only few of the affected cells in the target organs develop into tumors. Genetic analysis of nine pheochromocytomas from five unrelated patients with MEN 2 showed either duplication of the mutant RET allele in trisomy 10 or loss of the wild-type RET allele. Our results suggest a "second hit" causing a dominant effect of the mutant RET allele, through either duplication of the mutant allele or loss of the wild-type allele, as a possible mechanism for pheochromocytoma tumorigenesis in patients with MEN 2.

Constitutional von Hippel-Lindau (VHL) gene deletions detected in VHL families by fluorescence in situ hybridization.

von Hippel-Lindau (VHL) disease is an autosomal dominantly inherited cancer syndrome predisposing to a variety of tumor types that include retinal hemangioblastomas, hemangioblastomas of the central nervous system, renal cell carcinomas, pancreatic cysts and tumors, pheochromocytomas, endolymphatic sac tumors, and epididymal cystadenomas [W. M. Linehan et al., J. Am. Med. Assoc., 273: 564-570, 1995; E. A. Maher and W. G. Kaelin, Jr., Medicine (Baltimore), 76: 381-391, 1997; W. M. Linehan and R. D. Klausner, In: B. Vogelstein and K. Kinzler (eds.), The Genetic Basis of Human Cancer, pp. 455-473, McGraw-Hill, 1998]. The VHL gene was localized to chromosome 3p25-26 and cloned [F. Latif et al., Science (Washington DC), 260: 1317-1320, 1993]. Germline mutations in the VHL gene have been detected in the majority of VHL kindreds. The reported frequency of detection of VHL germline mutations has varied from 39 to 80% (J. M. Whaley et al., Am. J. Hum. Genet., 55: 1092-1102, 1994; Clinical Research Group for Japan, Hum. Mol. Genet., 4: 2233-2237, 1995; F. Chen et al., Hum. Mutat., 5: 66-75, 1995; E. R. Maher et al., J. Med. Genet., 33: 328-332, 1996; B. Zbar, Cancer Surv., 25: 219-232, 1995). Recently a quantitative Southern blotting procedure was found to improve this frequency (C. Stolle et al., Hum. Mutat., 12: 417-423, 1998). In the present study, we report the use of fluorescence in situ hybridization (FISH) as a method to detect and characterize VHL germline deletions. We reexamined a group of VHL patients shown previously by single-strand conformation and sequencing analysis not to harbor point mutations in the VHL locus. We found constitutional deletions in 29 of 30 VHL patients in this group using cosmid and P1 probes that cover the VHL locus. We then tested six phenotypically normal offspring from four of these VHL families: two were found to carry the deletion and the other four were deletion-free. In addition, germline mosaicism of the VHL gene was identified in one family. In sum, FISH was found to be a simple and reliable method to detect VHL germline deletions and practically useful in cases where other methods of screening have failed to detect a VHL gene abnormality.

"Molecular rulers" for calibrating phenotypic effects of telomere imbalance.

As a result of the increasing use of genome wide telomere screening, it has become evident that a significant proportion of people with idiopathic mental retardation have subtle abnormalities involving the telomeres of human chromosomes. However, during the course of these studies, there have also been telomeric imbalances identified in normal people that are not associated with any apparent phenotype. We have begun to scrutinize cases from both of these groups by determining the extent of the duplication or deletion associated with the imbalance. Five cases were examined where the telomere rearrangement resulted in trisomy for the 16p telomere. The size of the trisomic segment ranged from approximately 4-7 Mb and the phenotype included mental and growth retardation, brain malformations, heart defects, cleft palate, pancreatic insufficiency, genitourinary abnormalities, and dysmorphic features. Three cases with telomeric deletions without apparent phenotypic effects were also examined, one from 10q and two from 17p. All three deletions were inherited from a phenotypically normal parent carrying the same deletion, thus without apparent phenotypic effect. The largest deletion among these cases was approximately 600 kb on 17p. Similar studies are necessary for all telomeric regions to differentiate between those telomeric rearrangements that are pathogenic and those that are benign variants. Towards this goal, we are developing "molecular rulers" that incorporate multiple clones at each telomere that span the most distal 5 Mb region. While telomere screening has enabled the identification of telomere rearrangements, the use of molecular rulers will allow better phenotype prediction and prognosis related to these findings.

Genetic and histologic studies of somatomammotropic pituitary tumors in patients with the "complex of spotty skin pigmentation, myxomas, endocrine overactivity and schwannomas" (Carney complex).

Carney complex (CNC) is a familial multiple neoplasia and lentiginosis syndrome with features overlapping those of McCune-Albright syndrome (MAS) and other multiple endocrine neoplasia (MEN) syndromes, MEN type 1 (MEN 1), in particular. GH-producing pituitary tumors have been described in individual reports and in at least two large CNC patient series. It has been suggested that the evolution of acromegaly in CNC resembles that of the other endocrine manifestations of CNC in its chronic, often indolent, progressive nature. However, histologic and molecular evidence has not been presented in support of this hypothesis. In this investigation, the pituitary glands of eight patients with CNC and acromegaly [age, 22.9+/-11.6 yr (mean +/- SD)] were studied histologically. Tumor DNA was used for comparative genomic hybridization (CGH) (four tumors). All tumors stained for both GH and prolactin PRL (eight of eight), and some for other hormones, including alpha-subunit. Evidence for somatomammotroph hyperplasia was present in five of the eight patients in proximity to adenoma tissue; in the remaining three only adenoma tissue was available for study. CGH showed multiple changes involving losses of chromosomal regions 6q, 7q, 11p, and 11q, and gains of 1pter-p32, 2q35-qter, 9q33-qter, 12q24-qter, 16, 17, 19p, 20p, 20q, 22p and 22q in the most aggressive tumor, an invasive macroadenoma; no chromosomal changes were seen in the microadenomas diagnosed prospectively (3 tumors). We conclude that, in at least some patients with CNC, the pituitary gland is characterized by somatotroph hyperplasia, which precedes GH-producing tumor formation, in a pathway similar to that suggested for MAS-related pituitary tumors. Three GH-producing microadenomas showed no genetic changes by CGH, whereas a macroadenoma in a patient, whose advanced acromegaly was not cured by surgery, showed extensive CGH changes. We speculate that these changes represent secondary and tertiary genetic "hits" involved in pituitary oncogenesis. The data (1) underline the need for early investigation for acromegaly in patients with CNC; (2) provide a molecular hypothesis for its clinical progression; and (3) suggest a model for MAS- and, perhaps, MEN 1-related GH-producing tumor formation.

Pituitary macroadenoma in a 5-year-old: an early expression of multiple endocrine neoplasia type 1.

Multiple endocrine neoplasia type 1 (MEN 1) is associated with parathyroid, enteropancreatic, pituitary, and other tumors. The MEN1 gene, a tumor suppressor, is located on chromosome 11. Affected individuals inherit a mutated MEN1 allele, and tumorigenesis in specific tissues follows inactivation of the remaining MEN1 allele. MEN 1-associated endocrine tumors usually become clinically evident in late adolescence or young adulthood, as high levels of PTH, gastrin, or PRL. Because each of these tumors can usually be controlled with medications and/or surgery, MEN 1 has been regarded mainly as a treatable endocrinopathy of adults. Unlike in MEN 2, early testing of children in MEN 1 families is not recommended. We report a 2.3-cm pituitary macroadenoma in a 5-yr-old boy with familial MEN 1. He presented with growth acceleration, acromegaloid features, and hyperprolactinemia. We tested systematically to see whether his pituitary tumor had causes similar to or different from a typical MEN 1 tumor. Germ line DNA of the propositus and his affected relatives revealed a heterozygous point mutation in the MEN1 gene, which leads to a His139Asp (H139D) amino acid substitution. The patient had no other detectable germ-line mutations on either MEN1 allele. DNA sequencing and fluorescent in situ hybridization with a MEN1 genomic DNA sequence probe each demonstrated one copy of the MEN1 gene to be deleted in the pituitary tumor and not in normal DNA, proving MEN1 "second hit" as a tumor cause. Gsalpha mutation, common in nonhereditary GH-producing tumors, was not detected in this tumor. We conclude that this pituitary macroadenoma showed molecular genetic features of a typical MEN 1-associated tumor. This patient represents the earliest presentation of any morbid endocrine tumor in MEN 1. A better understanding of early onset MEN 1 disease is needed to formulate recommendations for early MEN 1 genetic testing.

Chromosome 8p deletion is associated with metastasis of human hepatocellular carcinoma when high and low metastatic models are compared.

Recently, we found that chromosome 8p deletion might be associated with hepatocellular carcinoma (HCC) metastasis by analyzing the differences in chromosomal alterations between primary tumors and their matched metastatic lesions of HCC with comparative genomic hybridization (CGH) (Qin et al. 1999). To further confirm this interesting finding, the genomic changes of two models bearing human HCC with different metastatic potentials (LCI-D20 and LCI-D35), and the new human HCC cell line with high metastatic potential (MHCC97) were analyzed by CGH. Gains on 1q, 6q, 7p, and 8q, and losses on 13p, 14p, 19p, 21, and 22 were detected in both LCI-D20 and LCI-D35 models. However, high copy number amplification of a minimum region at 1q12-q22 and 12q, and deletions on 1p32-pter, 3p21-pter, 8p, 9p, 10q, 14q, and 15p were detected only in the LCI-D20 model. Gains on 1p21-p32, 2p13-p21, 6p12-pter, 9p, 15q, and 16q11-q21, and losses on 2p23-pter, 4q24-qter, 7q31-qter, 12q, 17p, and 18 were detected only in the LCI-D35 model. The chromosomal aberration patterns in the MHCC97 cell line were similar to its parent LCI-D20 model, except that gains on 19q and losses on 4, 5, 10q, and 13q were found only in the cell line. These results provide some indirect clues to the metastasis-related chromosomal aberrations of HCC and further support the finding that 8p deletion is associated with HCC metastasis. 1q12-22 and 12q might harbor a novel oncogene(s) that contributes to the development and progression of HCC. Amplification on 8q and deletions on 4q and 17p may be not necessary for HCC metastasis.

Fluorescence in situ hybridization : application in cancer research and clinical diagnostics.

An opportunity to look inside of the individual cell for the direct visualization in situ of "what happened?" is the most wonderful feature offered by fluorescence in situ hybridization (FISH). DNA in situ hybridization is a technique that allows the visualization of defined sequences of nucleic acids within the individual cells. The method is based on the site specific annealing (hybridization) of single-stranded labeled DNA fragments (probes) to denatured, homologous sequences (targets) on cytological preparations, like metaphase chromosomes, interphase nuclei, or naked chromatin fibers. Visualization of hybridization sites becomes possible after detection steps by using a wide spectrum of the fluorescent dyes available.

Photon-counting technique for rapid fluorescence-decay measurement.

We report on a novel laser-induced fluorescence triple-integration method (LIFTIME) that is capable of making rapid, continuous fluorescence lifetime measurements by a unique photon-counting technique. The LIFTIME has been convolved with picosecond time-resolved laser-induced fluorescence, which employs a high-repetition-rate mode-locked laser, permitting the eventual monitoring of instantaneous species concentrations in turbulent flames. We verify the technique by application of the LIFTIME to two known fluorescence media, diphenyloxazole (PPO) and quinine sulfate monohydrate (QSM). PPO has a fluorescence lifetime of 1.28 ns, whereas QSM has a fluorescence lifetime that can be varied from 1.0 to 3.0 ns. From these liquid samples we demonstrate that fluorescence lifetime can currently be monitored at a sampling rate of up to 500 Hz with less than 10% uncertainty (1 sigma) .

Chromosomal and regional localization of the genes for UMPH2, APRT, PEPD, PEPS, PSP, and PGP in mink: comparison with man and mouse.

Segregation of mink biochemical markers uridine 5'-monophosphate phosphohydrolase-2 (UMPH2), adenine phosphoribosyltransferase (APRT), phosphoserine phosphatase (PSP), phosphoglycolate phosphatase (PGP), peptidases D (PEPD) and S (PEPS), as well as mink chromosomes, was investigated in a set of mink x mouse hybrid clones. The results obtained allowed us to make the following mink gene assignments: UMPH2, chromosome 8; PEPD and APRT, chromosome 7; PEPS, chromosome 6; and PSP and PGP, chromosome 14. The latter two genes are the first known markers for mink chromosome 14. For regional mapping, UMPH2 was analyzed in mouse cell clones transformed by means of mink metaphase chromosomes (Gradov et al., 1985) and also in mink x mouse hybrid clones carrying fragments of mink chromosome 8 of different sizes. Based on the data obtained, the gene for UMPH2 was assigned to the region 8pter----p26 of mink chromosome 8. The present data is compared with that previously established for man and mouse with reference to the conservation of syntenic gene groups and G-band homoeologies of chromosomes in mammals.

The X-autosome translocation in the common shrew (Sorex araneus L.): late replication in female somatic cells and pairing in male meiosis.

Common shrews have an XX/XY1Y2 sex chromosome system, with the "X" chromosome being a translocation (tandem fusion) between the "original" X and an autosome; in males this autosome is represented by the Y2 chromosome. From G-banded chromosomes, the Y2 is homologous to the long arm and centromeric part of the short arm of the X. The region of the X that is homologous to the Y2 and also the telomeric region of the short arm of the X were found to be early replicating in somatic cells from a female shrew after 5-bromo-2'-deoxyuridine (BrdU) treatment in vitro. The remainder of the short arm of the X was shown to be late replicating. Electron microscopic examination of synaptonemal complexes in males at pachytene revealed pairing of the Y2 axis with the long arm of the X, and Y1 with the short arm. At early stages of pachytene, there is apparently extensive nonhomologous pairing between the X and Y1. In essence, the short arm of the shrew X chromosome behaves like a typical eutherian X chromosome (it is inactivated in female somatic cells and is paried with the Y1 during male meiosis) while the long arm behaves like an autosome (escapes the inactivation and pairs with the Y2).

Subchromosomal localization and order of GLA, PGK1, HPRT, and G6PD loci on the X chromosome of the American mink (Mustela vison).

Segregation of the X-linked mink markers alpha-galactosidase (GLA), phosphoglycerate kinase-1 (PGK1), hypoxanthine phosphoribosyltransferase (HPRT), and glucose-6-phosphate dehydrogenase (G6PD) was analyzed in hybrids of gamma-irradiated mink fibroblasts and Chinese hamster cells and in hybrids of nonirradiated mink fibroblasts and mouse hepatoma cells. Based on this analysis, the order of the four genes is GLA-PGK1-HPRT-G6PD on the mink X chromosome. Cytogenetic analysis of five mink x Chinese hamster hybrid clones containing mink GLA, PGK1, and HPRT, but lacking G6PD, tentatively localized mink G6PD to Xq15.22----qter and also confirmed the gene order as GLA-PGK1-HPRT-G6PD-qter. Comparison of this order with its counterpart in man and the mouse, as well as an analysis of the G-band patterns of their X chromosomes, demonstrated putative similarities between mink and man and differences in the mouse. These differences may be due to a different rate of X-chromosomal rearrangement in mammalian evolution.

Regional assignments of eight genes on chromosome 2 in the American mink.

Chromosomal rearrangements involving mink chromosome 2 in mink-Chinese hamster and mink-mouse hepatoma somatic hybrids were identified. By means of these rearrangements, we assigned the genes for HK1, GOT1, and PP to 2pter----p22, those for PGD, PGM1 and ENO1 to 2q24.4----qter, and that for NP and ADK to 2pter----p11.1.

Transfer of mink genes into mouse cells by means of isolated lipid-encapsulated nuclei.

A method for gene transfer by means of interphase nuclei encapsulated within lipid membranes was developed. The method was based on passage of interphase nuclei through a layer of organic solvents containing phospholipids. Evidence was obtained indicating that the nuclei become surrounded by a protective phospholipid membrane: measurements of bound labelled or non-labelled phospholipids; decrease in the permeability of lipid-encapsulated nuclei for high molecular compounds; visualization by direct electron microscopy. Lipid-encapsulated nuclei of mink fibroblasts were used for transformation of mutant mouse LMTK- cells (deficient for thymidine kinase). The frequency of occurrence of HAT-resistant colonies/recipient cell was 1.9 X 10(-5). Biochemical analysis of 14 independent clones demonstrated that they all contained TK1 of mink origin. Analysis of 15 other biochemical markers located on 12 of the mink chromosomes revealed the activities of mink galactokinase (a syntenic marker) in 5 transformed clones, and that of mink aconitase-1 (the marker of mink chromosome 12) in 1 clone. No cytogenetically visible donor chromosomes were identified in the transformed clones. Nine transformed clones were tested for the stability of the TK+ phenotype; of these, the phenotype was expressed stably in 3 and unstably in 6. The method suggested is similar to the gene transfer procedure using total DNA. Its advantage is in ensuring efficient gene transfer and donor DNA integrity.

Regional assignment of the genes for TK1, GALK, ALDC, and ESD on chromosome 8 in the American mink by chromosome-mediated gene transfer.

A panel of clones of mink-Chinese hamster somatic cell hybrids was analysed to obtain data for assigning the genes for thymidine kinase-1 (TK1), galactokinase (GALK), subunit C of aldolase (ALDC), and esterase D (ESD) to specific mink chromosomes. The results demonstrate that the genes for TK1, GALK, ALDC and ESD are syntenic and located on mink chromosome 8. Prometaphase analysis of transformed mouse cells obtained by transfer of mink genes by means of metaphase chromosomes demonstrated the presence of mink chromosome 8 fragments of different sizes in some of the independent transformants. Segregation analysis of these fragments and mink TK1, GALK, ALDC and ESD allowed us to assign the genes for TK1 and GALK to 8p24, ALDC to pter-8p25, and ESD to 8q24-8qter.

Chromosome localization of the loci for PEPA, PEPB, PEPS, IDH1, GSR, MPI, PGM1, NP, SOD1, and ME1 in the common shrew (Sorex araneus).

This report extends the genetic map of the common shrew (Sorex araneus) by adding chromosome assignments for ten genes to the seven already mapped (Pack et al. 1995). A somatic cell hybrid panel was used for the mapping. The genes for peptidase A (PEPA) and isocitrate dehydrogenase-1 (IDH1) map to chromosome de; the genes for phosphoglucomutase-1 (PGM1), superoxide dismutase-1 (SOD1), and mannosephosphate isomerase (MPI) are located on chromosome af; the genes for nucleoside phosphorylase (NP) and glutathione reductase (GSR) are on chromosome ik; and the genes for peptidase S (PEPS), malic enzyme-1 (ME1), peptidase B (PEPB) are found on chromosomes jl, go, and mp respectively.