Familial medullary thyroid carcinoma and multiple endocrine neoplasia type 2B map to the same region of chromosome 10 as multiple endocrine neoplasia type 2A

Specific mutations of the RET proto-oncogene are related to disease phenotype in MEN 2A and FMTC

We have analysed 118 families with inherited medullary thyroid carcinoma (MTC) for mutations of the RET proto-oncogene. These included cases of multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B) and familial MTC (FMTC). Mutations at one of 5 cysteines in the extracellular domain were found in 97% of patients with MEN 2A and 86% with FMTC but not in MEN 2B patients or normal controls. 84% of the MEN2A mutations affected codon 634. MEN 2A patients with a Cys634 to Arg substitution had a greater risk of developing parathyroid disease than those with other codon 634 mutations. Our data show a strong correlation between disease phenotype and the nature and position of the RET mutation, suggesting that a simple, constitutive activation of the RET tyrosine kinase is unlikely to explain the events leading to MEN 2A and FMTC.

Rapid identification of overlapping YACs in the MEN2 region of human chromosome 10 by hybridization with Alu element-mediated PCR products

An overlapping set of 21 yeast artificial chromosomes (YACs) spanning the RET proto-oncogene [Takahashi et al., Oncogene 3 (1988) 571-578] and D10S102 markers on human chromosome 10 was isolated in a series of hybridization-based chromosomal walks in a YAC library. Genetic linkage analyses implicate this chromosomal region as the location of the gene (MEN2A) responsible for multiple endocrine neoplasia type 2A. Four YACs carrying a RET sequence-tagged site (STS) and two YACs carrying a D10S102 STS were used to initiate chromosome walks. These were based on hybridization of Alu element-mediated polymerase chain reaction (Alu-PCR) products from YACs to dot blots of Alu-PCR products from complex pools of YAC clones. The hybridization anchor content of YACs identified in the walks was confirmed by probing blots of Alu-PCR products from individual YACs and by comparing Alu-PCR fingerprints of each YAC. Ten hybridization-based Alu-PCR anchors and three STS anchors were ordered within eleven intervals created by the 21 overlapping YACs. The order of anchors requiring the fewest gaps in the YACs is consistent with the walking results and establishes the STS anchor order as D10S102-D10S94-RET. The overlapping set of YACs represents about 1.55 Mb of the human genome according to restriction mapping of four representative YACs in the contig. These results demonstrate the power of Alu-PCR hybridization for chromosomal walking and provide a rich source of overlapping YACs which can be used to identify candidate MEN2A genes.

Expression of the c-ret proto-oncogene during mouse embryogenesis

The c-ret proto-oncogene encodes a receptor tyrosine kinase whose normal function has yet to be determined. To begin to investigate the potential role of this gene in vertebrate development, we have isolated cDNA clones representing the murine c-ret gene, and have analyzed the pattern of expression during mouse embryogenesis, using northern blotting, in situ hybridization to histological sections and whole-mount hybridization histochemistry. c-ret transcripts were detected beginning at day 8.5 of embryogenesis, and were observed in a number of cell lineages in the developing peripheral and central nervous systems, as well as in the excretory system. In the cranial region at day 8.5-9.5, c-ret mRNA was restricted to a population of neural crest cells migrating from rhombomere 4 and forming the anlage of the facioacoustic ganglion, as well as to a closely associated domain of surface ectoderm and pharyngeal endoderm. At later stages (10.5-14.5 days), c-ret mRNA was observed in all cranial ganglia. In the peripheral nervous system of the trunk, c-ret was expressed in the autonomic ganglia and in subsets of cells in the dorsal root ganglia. In the enteric nervous system, c-ret was expressed in the presumptive enteric neuroblasts of the vagal crest (day 9.0-11.5), and in the myenteric ganglia of the gut (day 13.5-14.5). c-ret mRNA was observed in several regions of the central nervous system, including the undifferentiated neuroepithelial cells of the ventral neural tube (8.5 days), the motor neurons in the spinal cord and the hindbrain (10.5-14.5 days), the embryonic neuroretina (day 13.5) and the layers of the postnatal retina containing ganglion, amacrine and horizontal cells. Outside the nervous system, c-ret was expressed in the nephric (Wolffian) duct at day 8.5-10.5, the ureteric bud epithelium (but not the surrounding metanephric mesenchyme) at day 11.0-11.5, and the growing tips of the renal collecting ducts (but not the previously formed, subcortical portions of the collecting ducts, or the mesenchyme-derived renal vesicles) at day 13.5-17.5. Our results suggest that the c-ret gene may encode the receptor for a factor involved in the proliferation, migration, differentiation or survival of a variety of neuronal cell lineages, as well as in inductive interactions during organogenesis of the kidney.

Construction of radiation-reduced hybrids and their use in mapping of microclones from chromosome 10p11.2-q11.2

Radiation-reduced hybrids for mapping of DNA markers in the pericentromeric region of chromosome 10 were developed. A Chinese hamster/human somatic cell hybrid (762-8A) carrying chromosomes 10 and Y as the only human material were exposed to 40,000 rads of irradiation and then rescued by fusion with non-irradiated recipient Chinese hamster cells (GM459). Southern hybridization analyses revealed that 10 of 128 HAT-resistant clones contained human chromosomal fragments corresponding to at least one marker locus between FNRB (10p-11.2) and RBP3 (10q11.2). These hybrids were then used to map micro-dissection clones previously isolated and roughly mapped to this chromosomal region by fluorescence in situ hybridization (FISH). Two of the six microclones studied could be mapped to the proximity of the D10-S102 locus. These radiation hybrids are useful for the construction of refined genetic maps of the pericentromeric region of chromosome 10.

Screening and surgical intervention in the multiple endocrine neoplasia patient

Persons with multiple endocrine neoplasias (MEN) are a unique group of patients that present with various APUDomas. Screening of family members can lead to early detection of these tumors and possible cure of potentially fatal tumors. Screening for the MEN syndromes at present is limited to provocative and biochemical parameters. The gene(s) responsible for these syndromes have not, as of yet, been characterized but in the future will add greatly to the ability to identify these patients early. Early surgical intervention of these APUDomas, has lead to an improved prognosis for these tumors. The screening and the surgical approach to each syndrome are outlined.

A gene for Hirschsprung disease maps to the proximal long arm of chromosome 10

Hirschsprung disease (HSCR) is a frequent congenital disorder (1 in 5,000 newborns) of unknown origin characterized by the absence of parasympathetic intrinsic ganglion cells of the hindgut. Taking advantage of a proximal deletion of chromosome 10q (del 10q11.2-q21.2) in a patient with total colonic aganglionosis, and of a high-density genetic map of microsatellite DNA markers, we performed genetic linkage analysis in 15 non-syndromic long-segment and short-segment HSCR families. Multipoint linkage analysis indicated that the most likely location for a HSCR locus is between loci D10S208 and D10S196, suggesting that a dominant gene for HSCR maps to 10q11.2, a region to which other neural crest defects have been mapped.

A gene for Hirschsprung disease (megacolon) in the pericentromeric region of human chromosome 10

Hirschsprung disease (HSCR) is characterized by a congenital absence of enteric ganglia along a variable length of the intestine. Although long considered to be a multifactorial disease, we have identified linkage in a subset of five HSCR families to the pericentromeric region of chromosome 10, thereby providing monogenic inheritance in some families. A maximum two-point lod score of 3.37 (theta = 0.045) was observed between HSCR and D10S176, under an incompletely penetrant dominant model. Multipoint, affecteds-only and non-parametric analyses supported this finding and localize this gene to a region of approximately 7 centiMorgans, in close proximity to the locus for multiple endocrine neoplasia type 2 (MEN2). The co-occurrence of these two entities in some families might be attributable to shared pathogenetic origins.

Genetics of cancer predisposition and progression

The development of human cancer is a multistep process that entails a progressively more malignant phenotype through the evolution of cellular subsets with increasing numbers of genetic alterations. Here we review the molecular genetics of human cancer predisposition and progression and describe paradigmatic cancer types and cancer syndromes. We also briefly consider the future impact of molecular biology on cancer diagnosis and treatment.

Cloning of a cDNA encoding sheep calcitonin from a thyroid C-cell library

A sheep thyroid C-cell cDNA library constructed in lambda ZAPII was screened with a probe specific for the human calcitonin (CT)-encoding gene (CT). Plaque lifts from a total of 6 x 10(4) recombinant plaques identified six overlapping cDNA clones, one of which was an 806-bp cDNA representing an almost full-length copy of the sheep CT mRNA. The nucleotide (nt) sequence consists of a 71-bp 5'-flanking sequence, a protein-coding region of 429 bp with a coding potential for a 143-amino-acid (aa) protein with a deduced M(r) of 15,888 and a 306-bp 3'-untranslated region. Northern blot analysis of sheep thyroid tissue revealed two major mRNAs with sizes of 0.9 and 0.65 kb. The sheep CT cDNA shows 71% similarity at the nt level to human CT and 58% identity at the predicted aa level.

Development of a sequence-tagged site for the centromere of chromosome 10: its use in cytogenetic and physical mapping

We sequenced the alphoid centromere probe p alpha 10RP8 (D10Z1), aligned it to three published consensus sequences, and developed a sequence-tagged site (STS), sJRH-2, based upon oligonucleotide primers having two 3' mismatches with these consensus sequences. Polymerase chain reaction (PCR) amplification using genomic DNA from a somatic cell hybrid panel representing all human chromosomes demonstrated amplification from only those cell lines containing chromosome 10. Fluorescence in situ hybridization of the amplified product demonstrated intense and specific hybridization of the PCR product to 10p11.1-q11.1. A human genomic yeast artificial chromosome (YAC) library was screened using the sJRH-2 PCR assay, and five clones were identified. Sequence analysis of one chimeric clone (consisting of DNA segments derived from chromosomes 5p and 10cen) confirmed specificity of the STS for the centromere of chromosome 10. sJRH-2 provides a convenient cytogenetic marker for chromosome 10, which will also be useful for physical mapping of the pericentromeric region of chromosome 10, a region that harbors the gene(s) for three forms of multiple endocrine neoplasia (types 2A, 2B, and familial medullary thyroid carcinoma). The GenBank accession number for the p alpha 10RP8 sequence is X63622.

Regional assignment of the gene coding for a human Graves' disease autoantigen to 10q21.3-q22.1

A cDNA coding for a human Graves' disease autoantigen (hGT) has been isolated from a thyroid expression library. Using this cDNA as a probe, the gene for hGT, previously assigned to chromosome 10, has been further localized to 10q21.3-q22.1 by non-isotopic in situ hybridization.

A 1.5-megabase yeast artificial chromosome contig from human chromosome 10q11.2 connecting three genetic loci (RET, D10S94, and D10S102) closely linked to the MEN2A locus

The genetic loci RET, D10S94, and D10S102 from human chromosome 10q11.2 are very closely linked to a locus responsible for the multiple endocrine neoplasia type 2 (MEN2A and MEN2B) and medullary thyroid carcinoma (MTC1) familial cancer syndromes. We have constructed a 1.5-megabase contig consisting of six genomic yeast artificial chromosome clones which include these loci and define their physical order. A critical crossover event has been identified within the map interval; this event places the MEN2A locus centromeric to D10S102 and defines the orientation of the physical map on the chromosome. The orientation of the contig and order of the markers are centromere-RET-D10S94-D10S102-telomere. In addition, a microsatellite repeat polymorphism with a heterozygosity of 71% at the RET locus and a restriction fragment length polymorphism with a heterozygosity of 42% detected by a lambda clone from the D10S94 locus have been developed for high-resolution genetic linkage mapping and predictive diagnostic testing. These data place three important markers on a contiguous physical map, narrow the MEN2 disease locus interval, and provide a framework for further candidate gene identification efforts. Placement of these genetic loci along a clone-based map and continued expansion of the contig will also facilitate efforts to determine the relationship of physical to genetic distance near the centromeres of human chromosomes.

Cytogenetic studies on 19 papillary thyroid carcinomas

Short-term cultures from 19 papillary thyroid adenocarcinomas revealed clonal numerical and/or structural chromosomal changes in 13 tumors, nonclonal abnormalities in one tumor, and only normal karyotypes in five tumors. Clonal abnormalities of chromosome 10 were present in three tumors, two of which had the translocation t(7;10)(q35;q21). Numerical abnormalities of chromosome 17 were detected in two tumors.

A cluster of CpG islands at D10S94, near the locus responsible for multiple endocrine neoplasia type 2A (MEN2A)

We report the characterization of a dense cluster of CpG islands at D10S94 in proximal 10q11.2. D10S94 is tightly linked to the gene responsible for multiple endocrine neoplasia type 2A (MEN 2A), a dominantly inherited tumor syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma, and/or parathyroid adenoma. To date, no recombinants between D10S94 and MEN2A have been identified. The gene(s) responsible for two additional dominantly inherited disorders involving cancer of the medullary thyroid, MEN 2B (MEN2B), and dominantly inherited MTC without additional clinical features (MTC1), also map to this region. The gene or genes responsible for these disorders may be located at or near the D10S94 locus. A 570-kb long-range restriction map has been generated by pulsed-field gel electrophoresis using probes developed during a 160-kb bidirectional cosmid walk at D10S94. Six CpG islands are clustered within a 180-kb region; five fall within a 145-kb NotI restriction fragment that is contained in its entirety in our cosmid contig. The SacII, SfiI, and NotI restriction maps for lymphoblast and cloned DNA are concordant. These CpG islands may represent the 5' ends of candidate genes for MEN2A, MEN2B, and/or MTC1. One gene designated mcs94-1, which is associated with one of the CpG islands in this cluster, has been isolated and characterized in detail.

Isolation and high-resolution mapping of new DNA markers from the pericentromeric region of chromosome 10

The gene responsible for multiple endocrine neoplasia type 2A (MEN 2A) has been localized to the pericentromeric region of chromosome 10. Several markers that fail to recombine with MEN2A have been identified, including D10Z1, D10S94, D10S97, and D10S102. Meiotic mapping in the MEN2A region is limited by the paucity of critical crossovers identified and by the dramatically reduced rates of recombination in males. Additional approaches to mapping loci in the pericentromeric region of chromosome 10 are required. We have undertaken the generation of a detailed physical map by radiation hybrid mapping. Here we report the development of a radiation hybrid panel and its use in the mapping of new DNA markers in pericentromeric chromosome 10. The radiation-reduced hybrids used for mapping studies all retain small subchromosomal fragments that include both D10S94 and D10Z1. One hybrid was selected as the source of DNA for cloning. One hundred five human recombinant clones were isolated from a lambda library made with pp11A DNA. We have completed regional mapping of 22 of those clones using our radiation hybrid mapping panel. Seven markers have been identified and, when taken together with previously meiotically mapped markers, define eight radiation hybrid map intervals between D10S34 and RBP3. The identical order is found for a number of these using either the radiation hybrid mapping panel or the meiotic mapping panel. We believe that this combination cloning and mapping approach will facilitate the precise positioning of new markers in pericentromeric chromosome 10 and will help in refining further the localization of MEN2A.

Localization of the nucleotide excision repair gene ERCC6 to human chromosome 10q11-q21

We have cloned the human DNA excision repair gene ERCC6 by virtue of its ability to correct the uv sensitivity of Chinese hamster overy cell mutant UV61. This mutant is a member of complementation group 6 of the nucleotide excision repair-deficient rodent mutants. By means of in situ hybridization and Southern blot analysis of mouse x human somatic cell hybrids, the gene was localized to human chromosome 10q11-q21. An RFLP detected within the ERCC6 locus can be helpful in linkage analysis.

Physical mapping of a 950-kb region surrounding a locus (D10S102) tightly linked to the MEN2A gene

We have constructed a long-range contig of cosmid and YAC clones around D10S102, a locus that is tightly linked to the gene responsible for multiple endocrine neoplasia type 2A (MEN2A). With D10S102 as a starting point, a 360-kb cosmid contig was constructed by bidirectional genomic walking, and at least six fragments from these cosmids showed high sequence homology to other species. Five YAC clones were also isolated at the D10S102 locus, and they formed a contig covering 950 kb of genomic DNA. Furthermore, we obtained six RFLP systems from the contig, which will serve as new resources for fine-scale genetic linkage mapping of the MEN2A locus.

Cytogenetic study of a papillary thyroid carcinoma with a rearranged chromosome 10

Cytogenetic findings of a multifocal papillary thyroid cancer and a metastatic lymph node from a 29-year-old white female patient are reported. Two clonal aberrations were observed: a trisomy 7 in one nodule, and a rearranged chromosome 10 in a separate nodule and in a lymph node. The rearrangement of 10q described here is similar to other published cases and is relevant for interpreting the molecular findings associated with thyroid cancer.

Medullary carcinoma of the thyroid: current diagnosis and management

Medullary thyroid carcinoma (MTC) accounts for 5-10% of thyroid malignancies and occurs in either a sporadic or a familial form. The familial form is inherited in an autosomal dominant pattern, and expressed clinically as multiple endocrine neoplasia (MEN), types IIa and IIb, or as familial MTC alone. This neoplasm is derived from the parafollicular or C-cells, and has the ability to secrete a variety of polypeptide hormones including calcitonin, which serves as a tumor marker for the presence of MTC. The development of a calcitonin radioimmunoassay and the screening of patients at risk for the familial forms of MTC allows the diagnosis of the neoplasm in an occult stage when total thyroidectomy results in virtually 100% cure. We will present our experience with the diagnosis, treatment, and postoperative follow-up of our patients with this interesting neoplasm.