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Infection with viruses, such as the lactate dehydrogenase-elevating virus (LDV), is known to trigger the onset of autoimmune anemia through the enhancement of the phagocytosis of autoantibody-opsonized erythrocytes by activated macrophages. Type I interferon receptor-deficient mice show enhanced anemia, which suggests a protective effect of these cytokines, partly through the control of type II interferon production. The development of anemia requires the expression of Fc gamma receptors (Fc gamma R) I, III, and IV. Whereas LDV infection decreases Fc gamma R III expression, it enhances Fc gamma R I and IV expression in wild-type animals. The LDV-associated increase in the expression of Fc gamma R I and IV is largely reduced in type I interferon receptor-deficient mice, through both type II interferon-dependent and -independent mechanisms. Thus, the regulation of the expression of Fc gamma R I and IV, but not III, by interferons may partly explain the exacerbating effect of LDV infection on anemia that results from the enhanced phagocytosis of IgG autoantibody-opsonized erythrocytes.

Early onset seizures are a hallmark of Dravet syndrome. Previous studies in rodent models have shown that the epileptic phenotype is caused by loss-of-function of voltage-gated Na(V)1.1 sodium channels, which are chiefly expressed in gamma-aminobutyric acid (GABA)ergic neurons. Recently, a possibly critical role has been attributed to the hippocampus in the seizure phenotype, as local hippocampal ablation of Na(V)1.1 channels decreased the threshold for hyperthermia-induced seizures. However, the effect of ablation of Na(V)1.1 channels restricted to cortical sites has not been tested. Here we studied local field potential (LFP) and behavior in mice following local hippocampal and cortical ablation of Scn1a, a gene encoding the alpha 1 subunit of Na(V)1.1 channels, and we compared seizure characteristics with those of heterozygous global knockout Scn1(-/+) mice. We found a high incidence of spontaneous seizures following either local hippocampal or cortical ablation, notably during a transient time window, similar to Scn1a(-/+) mice. Nonconvulsive seizure activity in the injected area was common and preceded generalized seizures. Moreover, mice were susceptible to hyperthermia-induced seizures. In conclusion, local ablation of Na(V)1.1 channels in the hippocampus and cortex results in focal seizure activity that can generalize. These data indicate that spontaneous epileptic activity may initiate in multiple brain regions in Dravet syndrome.

Therapy with tumor-specific Abs is common in the clinic but has limited success against solid malignancies. We aimed at improving the efficacy of this therapy by combining a tumor-specific Ab with immune-activating compounds. In this study, we demonstrate in the aggressive B16F10 mouse melanoma model that concomitant application of the anti-TRP1 Ab (clone TA99) with TLR3-7/8 or -9 ligands, and IL-2 strongly enhanced tumor control in a therapeutic setting. Depletion of NK cells, macrophages, or CD8+ T cells all mitigated the therapeutic response, showing a coordinated immune rejection by innate and adaptive immune cells. FcγRs were essential for the therapeutic effect, with a dominant role for FcγRI and a minor role for FcγRIII and FcγRIV. FcγR expression on NK cells and granulocytes was dispensable, indicating that other tumoricidal functions of NK cells were involved and implicating that FcγRI, -III, and -IV exerted their activity on macrophages. Indeed, F4/80+Ly-6C+ inflammatory macrophages in the tumor microenvironment displayed high levels of these receptors. Whereas administration of the anti-TRP1 Ab alone reduced the frequency of these macrophages, the combination with a TLR agonist retained these cells in the tumor microenvironment. Thus, the addition of innate stimulatory compounds, such as TLR ligands, to tumor-specific Ab therapy could greatly enhance its efficacy in solid cancers via optimal exploitation of FcγRs.

Cytomegalovirus (CMV)-based vaccine vectors are promising vaccine platforms because they induce strong and long-lasting immune responses. Recently it has been shown that vaccination with a mouse CMV (MCMV) vector expressing the melanoma-specific antigen TRP2 (MCMV-TRP2) protects mice against outgrowth of TRP2-positive B16 melanoma tumors, and this protection was dependent on the induction of IgG antibodies. Here we demonstrate that, although mice lacking all receptors for the Fc part of IgG (FcγRs) develop normal IgG responses after MCMV-TRP2 vaccination, the protection against B16 melanoma was completely abrogated, indicating that FcγRs are indispensable in the downstream effector pathway of the polyclonal anti-TRP2 antibody response. By investigating compound FcγR-deficient mouse strains and by using immune cell type-specific cell ablation we show that the IgG antibody-mediated tumor protection elicited by MCMV-TRP2 mainly depends on FcγRI expression on macrophages, whereas FcγRIV plays only a modest role. Thus, tumor-specific antibody therapy might benefit from combination therapy that recruits FcγRI-expressing pro-inflammatory macrophages to the tumor micro-environment.

Here we show, for the first time, spontaneous cortical spreading depolarization (CSD) events – the electrophysiological correlate of the migraine aura – in animals by using the first generated familial hemiplegic migraine type 3 (FHM3) transgenic mouse model. The mutant mice express L263V‐mutated α1 subunits in voltage‐gated NaV1.1 sodium channels (Scn1a L263V). CSDs consistently propagated from visual to motor cortex, recapitulating what has been shown in patients with migraine with aura. This model may be valuable for the preclinical study of migraine with aura and other diseases in which spreading depolarization is a prominent feature.

Duchenne muscular dystrophy (DMD) is a severe muscle-wasting disease generally caused by reading frame disrupting mutations in the DMD gene resulting in loss of functional dystrophin protein. The reading frame can be restored by antisense oligonucleotide (AON)-mediated exon skipping, allowing production of internally deleted, but partially functional dystrophin proteins as found in the less severe Becker muscular dystrophy. Due to genetic variation between species, mouse models with mutations in the murine genes are of limited use to test and further optimize human specific AONs in vivo. To address this we have generated the del52hDMD/mdx mouse. This model carries both murine and human DMD genes. However, mouse dystrophin expression is abolished due to a stop mutation in exon 23, while the expression of human dystrophin is abolished due to a deletion of exon 52. The del52hDMD/mdx model, like mdx, shows signs of muscle dystrophy on a histological level and phenotypically mild functional impairment. Local administration of human specific vivo morpholinos induces exon skipping and dystrophin restoration in these mice. Depending on the number of mismatches, occasional skipping of the murine Dmd gene, albeit at low levels, could be observed. Unlike previous models, the del52hDMD/mdx model enables the in vivo analysis of human specific AONs targeting exon 51 or exon 53 on RNA and protein level and muscle quality and function. Therefore, it will be a valuable tool for optimizing human specific AONs and genome editing approaches for DMD.

Extensive analysis of a variety of arthritis models in germline KO mice has revealed that all four receptors for the Fc part of IgG (FcγR) play a role in the disease process. However, their precise cell type–specific contribution is still unclear. In this study, we analyzed the specific role of the inhibiting FcγRIIb on B lymphocytes (using CD19Cre mice) and in the myeloid cell compartment (using C/EBPαCre mice) in the development of arthritis induced by immunization with either bovine or chicken collagen type II. Despite their comparable anti-mouse collagen autoantibody titers, full FcγRIIb knockout (KO), but not B cell–specific FcγRIIb KO, mice showed a significantly increased incidence and severity of disease compared with wild-type control mice when immunized with bovine collagen. When immunized with chicken collagen, disease incidence was significantly increased in pan-myeloid and full FcγRIIb KO mice, but not in B cell–specific KO mice, whereas disease severity was only significantly increased in full FcγRIIb KO mice compared with incidence and severity in wild-type control mice. We conclude that, although anti-mouse collagen autoantibodies are a prerequisite for the development of collagen-induced arthritis, their presence is insufficient for disease development. FcγRIIb on myeloid effector cells, as a modulator of the threshold for downstream Ab effector pathways, plays a dominant role in the susceptibility to collagen-induced arthritis, whereas FcγRIIb on B cells, as a regulator of Ab production, has a minor effect on disease susceptibility.

Mutations of the adenomatous polyposis coli (APC) gene predispose individuals to familial adenomatous polyposis (FAP), characterized by multiple tumours in the large intestine. Most mouse models heterozygous for truncating mutant Apc alleles mimic FAP, however, the intestinal tumours occur mainly in the small intestine. To model large intestinal tumours, we generated a new conditional Apc-mutant allele, Apc(15lox), with exon 15 flanked by loxP sites. Similar survival of Apc(1638N/15lox) and Apc(1638N/+) mice indicated that the normal function of Apc was not impaired by the loxP sites. Deletion of exon 15, encoding nearly all functional Apc domains and containing the polyadenylation signal, resulted in a mutant allele expressing low levels of a 74 kDa truncated Apc protein. Germ line Cre-mediated deletion of exon 15 resulted in Apc(delta 15/+) mice, showing a severe Apc(Min/+)-like phenotype characterized by multiple tumours in the small intestine and early lethality. In contrast, conditional Cre-mediated deletion of exon 15 specifically directed to the epithelia of distal small and large intestine of FabplCre;Apc(15lox/+) mice led to longer survival and to tumours that developed predominantly in the large intestine, mimicking human FAP-associated colorectal cancer and sporadic colorectal cancer. We conclude that the FabplCre;Apc(15lox/+) mouse should be an attractive model for studies on prevention and treatment of colorectal cancer.

Introduction CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) is a hereditary small vessel disease caused by mutations in the NOTCH3 gene, leading to toxic NOTCH3 protein accumulation in the small- to medium sized arterioles. The accumulation is systemic but most pronounced in the brain vasculature where it leads to clinical symptoms of recurrent stroke and dementia. There is no therapy for CADASIL, and therapeutic development is hampered by a lack of feasible clinical outcome measures and biomarkers, both in mouse models and in CADASIL patients. To facilitate pre-clinical therapeutic interventions for CADASIL, we aimed to develop a novel, translational CADASIL mouse model. Results We generated transgenic mice in which we overexpressed the full length human NOTCH3 gene from a genomic construct with the archetypal c.544C > T, p.Arg182Cys mutation. The four mutant strains we generated have respective human NOTCH3 RNA expression levels of 100, 150, 200 and 350 % relative to endogenous mouse Notch3 RNA expression. Immunohistochemistry on brain sections shows characteristic vascular human NOTCH3 accumulation in all four mutant strains, with human NOTCH3 RNA expression levels correlating with age at onset and progression of NOTCH3 accumulation. This finding was the basis for developing the ‘NOTCH3 score’, a quantitative measure for the NOTCH3 accumulation load. This score proved to be a robust and sensitive method to assess the progression of NOTCH3 accumulation, and a feasible biomarker for pre-clinical therapeutic testing. Conclusions This novel, translational CADASIL mouse model is a suitable model for pre-clinical testing of therapeutic strategies aimed at delaying or reversing NOTCH3 accumulation, using the NOTCH3 score as a biomarker. Electronic supplementary material The online version of this article (doi:10.1186/s40478-015-0268-1) contains supplementary material, which is available to authorized users.

According to the classical interpretation of Knudson's 'two-hit' hypothesis for tumorigenesis, the two 'hits' are independent mutation events, the end result of which is loss of a tumor suppressing function. Recently, it has been shown that the APC (adenomatous polyposis coli) gene does not entirely follow this model. Both the position and type of the second hit in familial adenomatous polyposis (FAP) polyps depend on the localization of the germline mutation. This non-random distribution of somatic hits has been interpreted as the result of selection for more advantageous mutations during tumor formation. However, the APC gene encodes for a multifunctional protein, and the exact cellular function upon which this selection is based is yet unknown. In this study, we have analyzed somatic APC point mutations and loss of heterozygosity (LOH) in 133 colorectal adenomas from six FAP patients. We observed that when germline mutations result in truncated proteins without any of the seven beta-catenin downregulating 20-amino-acid repeats distributed in the central domain of APC, the majority of the corresponding somatic point mutations retain one or, less frequently, two of the same 20-amino-acid repeats. Conversely, when the germline mutation results in a truncated protein retaining one 20-amino-acid repeat, most second hits remove all 20-amino-acid repeats. The latter is frequently accomplished by allelic loss. Notably, and in contrast to previous observations, in a patient where the germline APC mutation retains two such repeats, the majority of the somatic hits are point mutations (and not LOH) located upstream and removing all of the 20-amino-acid repeats. These results indicate selection for APC genotypes that are likely to retain some activity in downregulating beta-catenin signaling. We propose that this selection process is aimed at a specific degree of beta-catenin signaling optimal for tumor formation, rather than at its constitutive activation by deletion of all of the beta-catenin downregulating motifs in APC.

Familial adenomatous polyposis (FAP) can be considered as a condition of the whole body as extracolonic features derived from all the three embryonic lineages are recorded with varying frequency in addition to the presence of multiple adenomas in the large intestine. Here, we describe two unrelated cases of FAP with unusual extracolonic phenotypes, namely several abnormalities of mesodermal origin strongly resembling Marfan syndrome (MFS) or a Marfan-like habitus. Conventional cytogenetic and FISH analysis did not reveal any gross chromosomal rearrangement on the long arm of chromosome 5 where the APC and FBN2 genes were located. However, in case 2 the FAP-causing mutation in the APC gene was found in the donor splice site of exon 4 and was shown to result in a frameshift and a premature termination codon. We propose that such connective tissue abnormalities may result from germline APC mutations in combination with specific genetic and/or environmental modifying factors.

Familial adenomatous polyposis (FAP) is an inherited predisposition to colorectal cancer caused by germline mutations in the adenomatous polyposis coli (APC) gene located on chromosome segment 5q21-q22. We detected a germline rearrangement of the APC gene in a Dutch FAP family by screening genomic DNA samples with APC cDNA probes. Subsequent molecular and cytogenetic studies revealed a constitutional reciprocal translocation t(5; 10) (q22; q25) that resulted in the disruption of the APC gene. Southern blot and polymorphic marker analysis indicated that part of the APC gene had been deleted. Analysis of the APC protein product indicated that the translocation breakpoint did not lead t o the formation of a detectable truncated APC protein but apparently resulted in a null allele. Evaluation of the clinical phenotypes in the patients suggested that they exhibited features of an unusual form of FAP characterized by a slightly delayed age of onset of colorectal cancer and a reduced number of colorectal polyps. The latter were mainly sessile and were located predominantly in the proximal colon. To our knowledge, this is the first description of FAP caused by a reciprocal translocation disrupting the APC gene. © 1995 Wiley-Liss, Inc.

Fc gamma RIIB-deficient mice generated in 129 background (Fc gamma RIIB(129)(-/-)) if back-crossed into C57BL/6 background exhibit a hyperactive phenotype and develop lethal lupus. Both in mice and humans, the Fc gamma r2b gene is located within a genomic interval on chromosome 1 associated with lupus susceptibility. In mice, the 129-derived haplotype of this interval, named Sle16, causes loss of self-tolerance in the context of the B6 genome, hampering the analysis of the specific contribution of Fc gamma RIIB deficiency to the development of lupus in Fc gamma RIIB(129)(-/-) mice. Moreover, in humans genetic linkage studies revealed contradictory results regarding the association of "loss of function" mutations in the Fc gamma r2b gene and susceptibility to systemic lupus erythematosis. In this study, we demonstrate that Fc gamma RIIB(-/-) mice generated by gene targeting in B6-derived ES cells (Fc gamma RIIB(B6)(-/-)), lacking the 129-derived flanking Sle16 region, exhibit a hyperactive phenotype but fail to develop lupus indicating that in Fc gamma RIIB(129)(-/-) mice, not Fc gamma RIIB deficiency but epistatic interactions between the C57BL/6 genome and the 129-derived Fc gamma r2b flanking region cause loss of tolerance. The contribution to the development of autoimmune disease by the resulting autoreactive B cells is amplified by the absence of Fc gamma RIIB, culminating in lethal lupus. In the presence of the Yaa lupus-susceptibility locus, Fc gamma RIIB(B6)(-/-) mice do develop lethal lupus, confirming that FcgRIIB deficiency only amplifies spontaneous autoimmunity determined by other loci. The Journal of Immunology, 2011, 187: 1304-1313.

Turcot syndrome (TS) is a rare genetic disease in which brain tumors occur in association with colonic polyposis. Since Turcot's original description in 1959, there have been disagreements about the mode of inheritance as well as the clinical expression of this condition. Some investigators maintain that TS is a phenotypic variant of the autosomal dominant familial adenomatous polyposis (FAP), while others observe that there are clinical differences between TS and FAP, and that the pattern of inheritance of TS is autosomal recessive. The distribution of persons with colonic lesions in a family with a patient of colonic polyposis and a brain tumor, described in this report, favored the recessive hypothesis. In this family, the involvement of the FAP gene on chromosome 5q21–q22 could be excluded by a linkage study using a panel of FAP-linked DNA markers. This finding, which indicates the occurrence of another polyposis gene elsewhere in the genome, will have consequences for the presymptomatic diagnosis of FAP by linked DNA markers. We conclude that TS is a distinct clinical-genetical entity with the triad of atypical polyposis coli, CNS tumors, and a recessive mode of inheritance. © 1992 Wiley-Liss, Inc.

Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant hereditary predisposition to the development of multiple colorectal adenomas and of a broad spectrum of extra-intestinal tumors. Moreover, somatic APC mutations play a rate-limiting and initiating role in the majority of sporadic colorectal cancers. Notwithstanding its multifunctional nature, the main tumor suppressing activity of the APC gene resides in its ability to regulate Wnt/β-catenin signaling. Notably, genotype–phenotype correlations have been established at the APC gene between the length and stability of the truncated proteins encoded by different mutant alleles, the corresponding levels of Wnt/β-catenin signaling activity they encode for, and the incidence and distribution of intestinal and extra-intestinal tumors. Here, we report a novel mouse model, Apc1572T, obtained by targeting a truncated mutation at codon 1572 in the endogenous Apc gene. This hypomorphic mutant allele results in intermediate levels of Wnt/β-catenin signaling activation when compared with other Apc mutations associated with multifocal intestinal tumors. Notwithstanding the constitutive nature of the mutation, Apc +/1572T mice have no predisposition to intestinal cancer but develop multifocal mammary adenocarcinomas and subsequent pulmonary metastases in both genders. The histology of the Apc1572T primary mammary tumours is highly heterogeneous with luminal, myoepithelial, and squamous lineages and is reminiscent of metaplastic carcinoma of the breast in humans. The striking phenotype of Apc +/1572T mice suggests that specific dosages of Wnt/β-catenin signaling activity differentially affect tissue homeostasis and initiate tumorigenesis in an organ-specific fashion., Author Summary Although signal transduction pathways are often described as “on–off” systems, the more quantitative aspects of signalling are likely to represent a very important means of regulation of the downstream biological outcomes. Mutations in members of the canonical Wnt signaling pathway represent among the most common defects in human cancers. However, it is yet unclear which factors determine tissue and organ specificity of the tumours arising upon Wnt constitutive activation. Previously, we have generated a series of hypomorphic alleles at the Apc tumor suppressor gene and showed that the differentiation potential of embryonic stem cells is dependent on the dosage of Wnt/β-catenin signalling these mutants encode for. Likewise, analysis of the two mutational hits occurring at the Apc gene in human and mouse intestinal tumors showed that these are selected to retain specific residual dosages of β-catenin downregulation. Here, we provide further support for this “just-right” signalling model by targeting a germline Apc mutation encoding for very low levels of Wnt signalling activation when compared with other mutants known to trigger intestinal tumorigenesis. Notwithstanding the constitutive nature of this mutation, heterozygous mice show a remarkable and highly penetrant predisposition to multifocal and metastatic mammary cancers without the GI tract tumor phenotype characteristic of the majority of Apc mouse models.

The APC gene, originally identified as the gene for familial adenomatous polyposis (FAP), is now considered as the true "gatekeeper" of colonic epithelial proliferation. Its main tumor suppressing activity seems to reside in the capacity to properly regulate intracellular beta-catenin signaling. Most somatic APC mutations are detected between codons 1286 and 1513, the mutation cluster region (MCR). This clustering can be explained either by the presence of mutation-prone sequences within the MCR, or by the selective advantage provided by the resulting truncated polypeptides. Here, a Msh2-deficient mouse model (Msh2(delta 7N) ) was generated and bred with Apc(1638N) and Apc(Min) that allowed the comparison of the somatic mutation spectra along the Apc gene in the different allelic combinations. Mutations identified in Msh2(delta 7N/delta 7N) tumors are predominantly dinucleotide deletions at simple sequence repeats leading to truncated Apc polypeptides that partially retain the 20 a.a. beta-catenin downregulating motifs. In contrast, the somatic mutations identified in the wild type Apc allele of Msh2(delta 7N/delta 7N) /Apc(+/1638N) and Msh2(delta 7N/delta 7N) /Apc(+/Min) tumors are clustered more to the 5' end, thereby completely inactivating the beta-catenin downregulating activity of APC. These results indicate that somatic Apc mutations are selected during intestinal tumorigenesis and that inactivation of the beta-catenin downregulating function of APC is likely to represent the main selective factor.

Background & Aims: Germline mutations in the adenomatous polyposis coli ( APC ) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant predisposition to the formation of multiple colorectal adenomas. Moreover, patients with FAP are at high risk of developing several extracolonic manifestations, including desmoids, cutaneous cysts, and tumors of the upper gastrointestinal tract. Although by definition desmoids are nonmalignant, because of their aggressive invasion of local structures, they represent one of the major causes of morbidity and mortality among patients with FAP. Methods: This study describes the histopathologic and molecular characterization of Apc 1638N, a mouse model for the broad spectrum of extracolonic manifestations characteristic of FAP. Results: Heterozygous Apc + /Apc 1638N animals develop fully penetrant and multifocal cutaneous follicular cysts and desmoid tumors in addition to attenuated polyposis of the upper gastrointestinal tract. Moreover, breeding of Apc + /Apc 1638N mice in a p53 -deficient background results in a dramatic sevenfold increase of the desmoid multiplicity. Conclusions: Because of the attenuated nature of their intestinal phenotype, these mice survive longer than other murine models for Apc -driven tumorigenesis. Therefore, Apc 1638N represents an ideal laboratory tool to test various therapeutic intervention strategies for the management of intestinal as well as extraintestinal tumors. GASTROENTEROLOGY 1998;114:275-283

Familial adenomatous polyposis (FAP) is an inherited predisposition to colorectal cancer characterized by the development of numerous adenomatous polyps predominantly in the colorectal region. Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for most cases of FAP. Mutations at the 5' end of APC are known to be associated with a relatively mild form of the disease, called attenuated adenomatous polyposis coli (AAPC). We identified a frameshift mutation in the 3' part of exon 15, resulting in a stop codon at 1862, in a large Dutch kindred with AAPC. Western blot analysis of lymphoblastoid cell lines derived from affected family members from this kindred, as well as from a previously reported Swiss family carrying a frameshift mutation at codon 1987 and displaying a similar attenuated phenotype, showed only the wild-type APC protein. Our study indicates that chain-terminating mutations located in the 3' part of APC do not result in detectable truncated polypeptides and we hypothesize that this is likely to be the basis for the observed AAPC phenotype.

Germ-line mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP). Genotype-phenotype correlation studies in patients with FAP have demonstrated associations of certain variants of the disease with mutations at specific sites within the APC gene. In a large FAP family, we identified a frameshift mutation located in the alternatively spliced region of exon 9. Phenotypic studies of affected family members showed that the clinical course of FAP was delayed, with gastrointestinal symptoms and death from colorectal carcinoma occurring on average 25 and 20 years later than usual, respectively. The numbers of colorectal adenomas differed markedly among affected individuals and the location of colorectal cancer lay frequently in the proximal colon. Our findings suggest that the exon 9 mutation identified in the pedigree is associated with late onset of FAP. The atypical phenotype may be explained by the site of the mutation in the APC gene. Analysis of the APC protein product indicated that the exon 9 mutation did not result in a detectable truncated APC protein. Given the location of the mutation within an alternatively spliced exon of APC, it is conceivable that normal APC proteins are produced from the mutant allele by alternative splicing.

Germ-line mutations in the human adenomatous polyposis coli (APC) gene result in familial adenomatous polyposis, an autosomal dominant disorder characterized by the early onset of multiple adenomatous polyps in the large bowel with a high likelihood of developing colorectal carcinomas. To understand the role of APC in intestinal tumor formation, we have introduced a chain-termination mutation in the 15th exon of the mouse Apc gene and employed it to modify the endogenous gene by homologous recombination in embryonic stem cells. Mice which are heterozygous for the Apc gene modification progressively develop intestinal tumors in a manner that is similar to that observed in patients with familial adenomatous polyposis and in mice which carry a mutation called multiple intestinal neoplasia (Min). Our results indicate that the Apc gene modification is a critical event in the initiation of intestinal tumor formation and results in an autosomal dominant predisposition toward development of spontaneous colonic and intestinal tumors in mice.

A number of polymorphic DNA markers on the long arm of chromosome 5, including C11p11, Pi227 and YN5.48, are known to be closely linked to the gene for familial adenomatous polyposis (FAP). C11p11 and Pi227 are localized centromeric to FAP. A critical Dutch pedigree revealed that YN5.48 is located on the other, telomeric, side of the FAP locus. This finding raises the reliability of presymptomatic diagnosis of FAP by linkage analysis to more than 99.9%. Genetic heterogeneity was considered to explain a small family in which the condition failed to segregate with C11p11.

Fifteen apparently unrelated Dutch families with familial adenomatous polyposis (FAP) also known as familial polyposis coli (FPC; McKusick No. 17510) were screened for linkage with the DNA probe C11p11 localized on chromosome 5q21-22 and previously reported to be closely linked to FAP (Bodmer et al. 1987; Leppert et al. 1987). In our study C11p11 was minimally informative, which is ascribable to its low heterozygosity in the North European populations. Of the above families, 12 were investigated also for linkage with D5S37 (DNA probe Pi227). Data from 11 of them were found to be informative and showed that FAP is closely linked to D5S37 previously localized on chromosome 5q21 (peak lod score 7.85 at a recombination fraction of 0.048 with 95% probability limits 0.005-0.145). Results discussed below indicate for the first time that the most likely location of the FAP gene is in the band 5q22 very close to 5q21, if not in the transitional zone between these two bands. The probe Pi227 recognizes 4 restriction fragment length polymorphism (RFLP) sites, exhibiting a total of 9 alleles with 24 theoretically possible haplotypes in the Dutch population. Therefore, this probe appears to have potential as a generally useful predictive marker for FAP until much closer and similarly useful markers become available.

Familial adenomatous polyposis (FAP) is a disorder with autosomal dominant inheritance, which predisposes to colorectal adenocarcinoma. The gene causing the disorder has been assigned to chromosome 5 by means of a polymorphic DNA marker called C11p11. An informative Dutch pedigree showed that two other linked polymorphic DNA markers, Pi227 and YN5.48, closely flank the FAP locus, one on either side. This finding will allow prenatal and presymptomatic diagnosis of FAP, with more than 99.9% reliability in the majority of families, by means of already available markers.