Deletion of chromosome 5q and familial adenomatous polyposis

Could APC Gene Screening be Useful in Children with Hepatoblastoma? Early Onset of Adenocarcinoma in a Child with Familial Adenomatous Polyposis and Hepatoblastoma

Familial adenomatous polyposis is an inherited disorder characterized by the development of hundreds of colorectal adenomas during adolescence, which in many cases will transform into colorectal cancer by the fourth decade of life, along with the development of various malignant tumors including hepatoblastoma. We report on a female patient with a de novo interstitial deletion of 5q21.3-q23.3, encompassing the APC gene, associated with adenomatous polyposis and early colorectal cancer, hepatoblastoma, epidermoid cysts, mental retardation, several mild dysmorphic signs and lower limb venous thrombosis.

Severe Mental Retardation Patient With a De Novo Chromosomal Deletion 5q14-22 Can Be a Carrier of a Rectal And Duodenal Cancer Associated With Over 200 Colorectal Polyps: A Case Report

Introduction

Familial adenomatous polyposis (FAP) caused by a de novo 5q chromosomal deletion is rare, and precise cytogenetic analysis using comparative genomic hybridization (CGH) arrays have been performed in a few cases.

Case presentation

We herein present the case of a 38-year-old man with advanced rectal and duodenal cancer, FAP, and severe mental retardation caused by a de novo chromosomal deletion at 5q14–22. He was referred to our outpatient clinic because of a positive fecal occult blood test result. He was found to have advanced rectal cancer, with over 200 colorectal polyps, and duodenal cancer. He underwent laparoscopic total proctocolectomy with definitive ileostomy followed by partial resection of the duodenum. Comparative genomic hybridization to characterize deleted genes identified a large 5q deletion expanding approximately 24.9 Mbp, including the APC gene.

Conclusion

Patients who harbor a chromosomal deletion involving 5q21 are at risk of developing rectal cancer and polyposis. Therefore, such patients need early cancer screening following the availability of genetic information.

Interstitial deletion 5p14.1-p15.2 and 5q14.3-q23.2 in a patient with clubfoot, blepharophimosis, arthrogryposis, and multiple congenital abnormalities

Interstitial deletions of the short and long arms of chromosome 5 are rare cytogenetic abnormalities. The 5p distal deletion is a genetic disorder characterized by a high-pitched cat-like cry, microcephaly, epicanthal folds, micrognathia, severe intellectual disability and motor delays. Previously, more than 46 patients with the 5q deletion have been reported. Here, we report de novo interstitial deletions involving 5p14.1-p15.2 and 5q14.3-q23.2 in a patient with multiple congenital abnormalities, including blepharophimosis, arthrogryposis, short neck, round face, pelvic kidney, agenesis of the corpus callosum, and clubfoot. The deletions were characterized using GTG banding and aCGH microarray analysis. Concurrent 5p and 5q interstitial deletions in humans have not been previously reported. We also discussed the relationship between the 5q deleted region and clubfeet.

APC conditional knock-out mouse is a model of infantile spasms with elevated neuronal β-catenin levels, neonatal spasms, and chronic seizures

Infantile spasms (IS) are a catastrophic childhood epilepsy syndrome characterized by flexion-extension spasms during infancy that progress to chronic seizures and cognitive deficits in later life. The molecular causes of IS are poorly defined. Genetic screens of individuals with IS have identified multiple risk genes, several of which are predicted to alter β-catenin pathways. However, evidence linking malfunction of β-catenin pathways and IS is lacking. Here, we show that conditional deletion in mice of the adenomatous polyposis coli gene (APC cKO), the major negative regulator of β-catenin, leads to excessive β-catenin levels and multiple salient features of human IS. Compared with wild-type littermates, neonatal APC cKO mice exhibit flexion-extension motor spasms and abnormal high-amplitude electroencephalographic discharges. Additionally, the frequency of excitatory postsynaptic currents is increased in layer V pyramidal cells, the major output neurons of the cerebral cortex. At adult ages, APC cKOs display spontaneous electroclinical seizures. These data provide the first evidence that malfunctions of APC/β-catenin pathways cause pathophysiological changes consistent with IS. Our findings demonstrate that the APC cKO is a new genetic model of IS, provide novel insights into molecular and functional alterations that can lead to IS, and suggest novel targets for therapeutic intervention.

Differences in neuropsychological and behavioral parameters and brain structure in patients with familial adenomatous polyposis: a sibling-paired study

Background

Familial adenomatous polyposis (FAP) is an autosomal dominant hereditary colon cancer syndrome caused by mutations in adenomatous polyposis coli (APC) with both colonic and extra-colonic manifestations. Case reports have noted an association with FAP and intellectual disability and animal studies have shown that APC is implicated in neural development and function, but no studies have investigated neuropsychological, behavioral, or structural brain characteristics of patients with FAP.

Methods

We undertook a pilot, sibling-pair study comparing three patients with FAP to their sex-matched siblings without FAP. Each sibling pair underwent neuropsychological testing by a blinded examiner, high resolution brain MRI scans, and the mother of each pair rated her children’s adaptive life skills and behavioral and emotional characteristics. Given the small number of study participants in this pilot study, quantitative comparisons of results were made by subtracting the score of the non-FAP sibling from the FAP patient on the various neuropsychological tests and parent rating questionnaires to calculate a difference, which was then divided by the standard deviation for each individual test to determine the difference, corrected for the standard deviation. Diffusion numbers in multiple regions of the brain as assessed by MRI were calculated for each study participant.

Results

We found similarity between siblings in all three pairs on a wide range of neuropsychological measures (general intelligence, executive function, and basic academic skills) as tested by the psychologist as well as in descriptions of adaptive life skills as rated by mothers. However, mothers’ ratings of behavioral and emotional characteristics of two of the three pairs showed differences between the siblings, specifically that the patients with FAP were found to have more behavioral and emotional problems compared to their siblings. No differences in brain structure were identified by MRI.

Conclusion

We report the first study exploring neuropsychological, behavioral, emotional, and structural brain characteristics of patients with FAP and found subjective differences as assessed by maternal perception in behavioral and emotional characteristics in patients with FAP compared to their siblings. Larger studies are needed to elucidate the relationship, if any, between FAP and brain function.

Adenomatous Polyposis Coli Protein Deletion in Efferent Olivocochlear Neurons Perturbs Afferent Synaptic Maturation and Reduces the Dynamic Range of Hearing

Normal hearing requires proper differentiation of afferent ribbon synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) that carry acoustic information to the brain. Within individual IHCs, presynaptic ribbons show a size gradient with larger ribbons on the modiolar face and smaller ribbons on the pillar face. This structural gradient is associated with a gradient of spontaneous rates and threshold sensitivity, which is essential for a wide dynamic range of hearing. Despite their importance for hearing, mechanisms that direct ribbon differentiation are poorly defined. We recently identified adenomatous polyposis coli protein (APC) as a key regulator of interneuronal synapse maturation. Here, we show that APC is required for ribbon size heterogeneity and normal cochlear function. Compared with wild-type littermates, APC conditional knock-out (cKO) mice exhibit decreased auditory brainstem responses. The IHC ribbon size gradient is also perturbed. Whereas the normal-developing IHCs display ribbon size gradients before hearing onset, ribbon sizes are aberrant in APC cKOs from neonatal ages on. Reporter expression studies show that the CaMKII-Cre used to delete the floxed APC gene is present in efferent olivocochlear (OC) neurons, not IHCs or SGNs. APC loss led to increased volumes and numbers of OC inhibitory dopaminergic boutons on neonatal SGN fibers. Our findings identify APC in efferent OC neurons as essential for regulating ribbon heterogeneity, dopaminergic terminal differentiation, and cochlear sensitivity. This APC effect on auditory epithelial cell synapses resembles interneuronal and nerve-muscle synapses, thereby defining a global role for APC in synaptic maturation in diverse cell types.

SIGNIFICANCE STATEMENT

This study identifies novel molecules and cellular interactions that are essential for the proper maturation of afferent ribbon synapses in sensory cells of the inner ear, and for normal hearing.

Adenomatous polyposis coli protein deletion leads to cognitive and autism-like disabilities

Intellectual disabilities (IDs) and autism spectrum disorders link to human APC inactivating gene mutations. However, little is known about adenomatous polyposis coli's (APC's) role in the mammalian brain. This study is the first direct test of the impact of APC loss on central synapses, cognition and behavior. Using our newly generated APC conditional knock-out (cKO) mouse, we show that deletion of this single gene in forebrain neurons leads to a multisyndromic neurodevelopmental disorder. APC cKO mice, compared with wild-type littermates, exhibit learning and memory impairments, and autistic-like behaviors (increased repetitive behaviors, reduced social interest). To begin to elucidate neuronal changes caused by APC loss, we focused on the hippocampus, a key brain region for cognitive function. APC cKO mice display increased synaptic spine density, and altered synaptic function (increased frequency of miniature excitatory synaptic currents, modestly enhanced long-term potentiation). In addition, we found excessive β-catenin levels and associated changes in canonical Wnt target gene expression and N-cadherin synaptic adhesion complexes, including reduced levels of presenilin1. Our findings identify some novel functional and molecular changes not observed previously in other genetic mutant mouse models of co-morbid cognitive and autistic-like disabilities. This work thereby has important implications for potential therapeutic targets and the impact of their modulation. We provide new insights into molecular perturbations and cell types that are relevant to human ID and autism. In addition, our data elucidate a novel role for APC in the mammalian brain as a hub that links to and regulates synaptic adhesion and signal transduction pathways critical for normal cognition and behavior.

Multidisciplinary treatment of desmoid tumours in Gardner's syndrome due to a large interstitial deletion of chromosome 5q

BACKGROUND AND AIMS

Classic autosomal-dominant familial adenomatous polyposis (FAP) is clinically defined by the development of hundreds to thousands of colorectal adenomas beginning in childhood and adolescence. A variant of FAP characterized by polyposis in combination with osteomas or soft tissue tumours is called Gardner's syndrome. FAP is caused by germline inactivation of the APC (adenomatous polyposis coli) tumour-suppressor gene located on the long arm of chromosome 5 (5q21-5q22). Cytogenetically visible deletions of chromosome 5q encompassing APC have very rarely been reported. Here, we aimed to phenotypically and genetically characterize a patient with a heterozygous 5q deletion resulting in Gardner's syndrome.

METHODS AND RESULTS

A 26-year-old female patient with mild mental handicap and dysmorphic features due to a cytogenetically visible deletion on chromosome 5q (microscopically estimated region 5q14-5q23) presented at our tertiary referral centre because of mild adenomatous polyposis (<500 polyps). Twenty months after prophylactic proctocolectomy with definitive ileostomy, three rapidly growing desmoids were observed. Tumour-associated complications necessitated a multidisciplinary approach including medical treatment, surgery and radiation therapy. The characterization of the deletion by comparative genomic hybridization identified a large 5q deletion expanding over a 20-Mb region (5q21.3-5q23.3) including the APC gene.

CONCLUSION

Chromosome deletions must be suspected in patients presenting with FAP together with mental handicap and dysmorphic features. This case also impressively shows that FAP-associated desmoids need multimodal treatment taking into account the patient's individual symptoms, disease progression and tumour location.

Familial adenomatous polyposis

A multimodal approach of complementary techniques targeting primarily truncating, deletion and rearrangement mutations provides a robust screening protocol that identifies the vast majority of pathogenic germline APC gene mutations in FAP patients. Patients in whom no mutation is identified through this mutation protocol, may be sub-cohorts representing a different FAP pathogenesis including MYH associated polyposis and somatic cell mosaicism for APC gene mutations.

Familial adenomatous polyposis in a patient with unexplained mental retardation

BACKGROUND

A 22-year-old woman was referred to a genomic medicine clinic for evaluation of suspected Prader-Willi syndrome (PWS) after normal DNA methylation studies on chromosome 15 were obtained. Features suggestive of PWS included mental retardation, short stature, obesity, hypotonia, and small hands and feet. The patient, however, lacked many PWS-defining behavioral features, including hyperphagia, compulsive skin picking, and food-seeking behaviors.

INVESTIGATIONS

DNA methylation studies on chromosome 15 were completed before the patient's presentation. At the genomic medicine clinic, she underwent standard karyotyping, array comparative genomic hybridization, fluorescent in situ hybridization analysis, colonoscopy, endoscopy, thyroid ultrasound, and thyroid fine needle aspiration biopsy.

DIAGNOSIS

Familial adenomatous polyposis with mental retardation, caused by an interstitial deletion of the long arm of chromosome 5 encompassing the APC (adenomatous polyposis coli) tumor suppressor locus.

MANAGEMENT

Colectomy with ileorectal anastomosis and thyroidectomy with subsequent iodine-131 therapy. The patient also underwent genetic counseling and was prescribed a program of caloric reduction and exercise.

Large deletions of the APC gene in 15% of mutation-negative patients with classical polyposis (FAP): a Belgian study

Germline mutations of the APC gene are responsible for familial adenomatous polyposis (FAP). Most of the mutations are protein truncating mutations and are spread over the coding region. Rare whole-gene deletions or exonic deletions have been described. From a series of 85 patients clinically diagnosed with FAP or attenuated FAP (AAPC) in our center, 30 (35%) were found to have truncating or missense mutations. We have now screened the remaining 55 patients for exonic deletions or duplications, first by semi-quantitative PCR and later by multiplex ligation-dependent probe amplification (MLPA). Three whole-gene deletions and one exon 14 deletion were found (5% of patients). The whole-gene deletions were confirmed by fluorescence in situ hybridization (FISH) analysis, and the breakpoints of the exon 14 deletion could be determined using long range PCR. Further characterization of the whole gene deletions was performed using extragenic polymorphic markers and/or semi-quantitative PCR. We could demonstrate that the deletions do not encompass the MCC gene. Interestingly, the phenotype of the deletion patients was not different from that of patients with truncating mutations. The polyp numbers ranged from attenuated to profuse polyposis and the interfamilial variability of disease phenotype was as in other FAP families. In none of the 28 AAPC patients included in this study, was a large deletion found, while 15% of the patients with classical polyposis had a genomic deletion. It corroborates recently published data, suggesting that large deletions may occur with a frequency higher than 10% in mutation-negative patients with a classical polyposis. In this article, we have included an overview of genomic rearrangements in the 5q21 region.

Molecular characterisation of a prenatally diagnosed 5q15q21.3 deletion and review of the literature

BACKGROUND

Ultrasound examination performed on a 32-year old woman at 30 weeks' gestation showed the presence of fetal malformations. Amniocentesis was performed.

METHODS AND RESULTS

Cytogenetic analysis of cultured amniocytes revealed an interstitial deletion of the long arm of chromosome 5. Molecular studies confirmed that the deletion included the 5q15-21.3 region and was 14 Mb in size. Therefore, the karyotype was: 46,XY,del(5)(q15q21.3). In addition, analysis of polymorphic DNA markers showed that the deletion was of paternal origin.

CONCLUSIONS

The pregnancy was terminated at 34 weeks' gestation. At autopsy, the fetus displayed dysmorphic features, thin limbs and renal abnormalities. The clinical findings observed in the fetus as well as in 20 cases reported previously allowed us to further delineate the phenotype of such interstitial 5q15q21.3 deletions.

Phenotypic and molecular characterisation of a de novo 5q deletion that includes the APC gene

We report on a 12-year-old female patient with mild dysmorphic signs, including bilateral epicanthal folds, low-set dysplastic ears, a short nose with anteverted nostrils, conically shaped fingers, generalised increase of subcutaneous fat, multiple fine venous teleangiectasia on her back, mild pectus carinatum, and a general muscular hypotonia. Cytogenetic analysis and fluorescence in situ hybridisation (FISH) studies using region-specific BAC and YAC clones indicated a de novo interstitial deletion of the long arm of chromosome 5, resulting in monosomy 5q21.1-q23.1. Molecular analysis of polymorphic markers helped to narrow down the breakpoints and demonstrated that the derivative chromosome 5 is of paternal origin. By using the same panel of polymorphic markers, a reinvestigation of a similar, already published, 5q deletion case [Raedle et al. (2001) Am J Gastroenterol 96:3016-3020] was performed, allowing a more detailed genotype-phenotype correlation. Phenotypic classification was also carried out. Several known genes, including APC and MCC, were found to map to the common deleted genomic segment. Genetic counselling based on the molecular analysis data was performed for the index family.

Familial adenomatous polyposis and mental retardation caused by a de novo chromosomal deletion at 5q15-q22: report of a case

Familial adenomatous polyposis, caused by mutations in the adenomatous polyposis coli gene located at chromosome 5q21, is an autosomal dominant syndrome characterized by polyposis of the colon and rectum and nearly 100 percent progression to colorectal cancer. We report a case of familial adenomatous polyposis and mental retardation caused by a chromosomal deletion at 5q15-q22. Chromosomal analysis is considered part of the evaluation of children with mental retardation and developmental delay. The resulting karyotypes from high-resolution chromosomal analysis can help characterize large deletions, some of which involve known tumor suppressor genes. Because familial adenomatous polyposis may arise from de novo chromosomal deletions involving the adenomatous polyposis coli gene locus, individuals with chromosomal deletions involving 5q21 should be considered at-risk for familial adenomatous polyposis and offered standard screening with flexible sigmoidoscopy by 10 to 12 years of age.

Interstitial deletion of the long arm of chromosome 5 in a boy with multiple congenital anomalies and mental retardation: Molecular characterization of the deleted region to 5q22.3q23.3

Interstitial deletions of the middle portion of the long arm of chromosome 5 are relatively rare. So far, only 36 cases have been reported. Because of the repetitive banding pattern of this region, the extent and localization of the deleted segment has not been well characterized in the majority of reported cases. This has complicated attempts to establish a definite karyotype-phenotype correlation. We report a further case with a de novo interstitial deletion of the region 5q?15 to 5q?22 identified by standard karyotype analysis. The proband presented with failure to thrive, developmental delay, distinct craniofacial dysmorphic features, and associated structural anomalies (amongst them cleft palate, iris colobomata, and horseshoe kidney, which have previously been reported in 5q deletion cases). In addition, this child had an Arnold-Chiari type I malformation that required surgical decompression. FISH studies using BAC clones spanning the 5q15 to 5q22 region revealed that these were all present in both homologues. Use of more distal clones allowed delineation of the deleted region to 5q22.3q23.3 and to narrow down the breakpoints to approximately 200 kb. The 14 Mb deleted region contains about 60 genes but, with the possible exception of FBN2 and DMXL1, there are no obvious candidate genes for the specific components of the phenotype. This case illustrates the discrepancy between cytogenetic and molecular techniques in trying to delineate 5q interstitial deletions. Molecular studies need to be performed on these patients, to establish genotype-phenotype correlation and to understand the role and influence of genes in this region.

Familial insertion (3;5)(q25.3;q22.1q31.3) with deletion or duplication of chromosome region 5q22.1-5q31.3 in ten unbalanced carriers

We report on the clinical and cytogenetic data of a large family with an unbalanced insertion translocation (3;5)(q25.3;q22.1q31.3). Analysis of GTG-banded chromosomes demonstrated that unbalanced inheritance of a parental insertion translocation caused either a partial deletion or duplication 5q in this family. The derivative chromosomes were characterized further using microdissection and FISH with band-specific probes. The clinical picture of the proband with a partial deletion of chromosome 5 was characterized by moderate psychomotor retardation, mild facial dysmorphism, cleft palate, and single transverse crease. The family members with a partial duplication of chromosome 5 were borderline intelligent, had mild facial dysmorphism, a cardiac anomaly, and a high-pitched voice. The unbalanced carriers were compared with patients reported in the literature with a duplication or deletion of chromosome region 5q22.1 --> 5q31.3.

Chromosome rearrangement with no apparent gene mutation in familial adenomatous polyposis and hepatocellular neoplasia

We have identified a constitutional inversion in chromosome 5 associated with familial adenomatous polyposis in three generations of a Mexican family. Two of three siblings developed hepatic neoplasia in infancy. The gene truncation assay failed to demonstrate a truncated protein in the segment harboring the adenomatous polyposis coli (APC) genes. Polymerase chain reaction (PCR) amplification of APC gene coding exons and sequencing of PCR products did not reveal any significant mutation. The data suggest that in this family, the phenotype may be the result of a "position effect."

A de novo deletion of chromosome 5q causing familial adenomatous polyposis, dysmorphic features, and mild mental retardation

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder that typically presents with colorectal cancer secondary to extensive adenomatous polyps of the colon. The molecular basis and clinical phenotype of FAP are well known. Recurrent episodes of severe abdominal pain and a positive fecal occult blood test in an 18-yr-old boy with mild mental retardation and slight dysmorphic features of the face, head, and skeletal system led to the diagnosis of FAP. The clinical workup revealed the presence of over 100 sessile colonic polyps but no polyp formation in the upper GI tract, no cancer development, nor other FAP-associated lesions. To find out whether there is an association between mental retardation and FAP we performed a chromosome analysis including comparative genomic hybridization and an indirect genotype analysis with polymorphic markers from the APC gene region. Cytogenetic analysis showed an interstitial deletion of chromosomal region 5q that was confined to the region 5q21-q22 by comparative genomic hybridization. The deletion, spanning about 10 centimorgans, encompassed the complete APC gene and can be considered as causative for FAP. Moreover, molecular genetic analysis with polymorphic markers flanking the APC gene demonstrated a de novo deletion on the paternal chromosome. Cytogenetically detectable deletions on chromosome 5 including the APC gene generally lead to an associated gene deletion syndrome. Individuals who present with mild mental retardation and dysmorphic features should therefore be investigated for chromosomal deletions. If the deletion encompasses the APC gene, these patients are at high risk of developing FAP and associated complications.

Attenuated familial adenomatous polyposis in a man with an interstitial deletion of chromosome arm 5q

Familial adenomatous polyposis (FAP) is an inherited colon cancer syndrome caused by mutations in the APC gene on chromosome region 5q21. Patients typically present with several hundred to several thousand polyps throughout the colon. Benign and malignant extracolonic manifestations are often present. Attenuated FAP (AFAP) is a recognized variant of FAP in which patients present with fewer than 100 polyps and appear to have a delayed onset of the clinical manifestations of FAP. Mutations in specific regions of the APC gene are associated with AFAP. A full deletion of the APC gene region has previously been thought to be associated with typical FAP. We now report on a 39-year-old man with a cytogenetically visible interstitial 5q deletion. Fluorescent in situ hybridization analysis with two cosmid probes specific for the 5' and 3' ends of the gene indicated that the entire APC locus is deleted. The number of polyps (50-60) seen in this patient was consistent with AFAP, as was the absence of multiple congenital hypertrophy of the retinal pigment epithelium (CHRPE). This is the first reported case of AFAP associated with a germline deletion of the entire APC gene.

Familial adenomatous polyposis: a submicroscopic deletion at the APC locus in a family with mentally normal patients

Cytogenetically visible deletions that include the adenomatosis polyposis coli (APC) locus have repeatedly been reported in mentally handicapped polyposis patients. We report on a family with a submicroscopic deletion of about 200 kb including more than the 3' half of the APC gene and the adjacent DP1 gene. The deletion was detected by linkage analysis with flanking and intragenic markers and proven by in situ hybridisation with intragenic cosmid clones. All the familial adenomatous polyposis (FAP) patients and persons at risk in the family show normal behaviour and intelligence. Thus, it is conceivable that at least some of the FAP patients in whom mutations could not be identified by routine methods may have large but submicroscopic deletions.

Familial pancreatic cancer and the genetics of pancreatic cancer

In our current understanding of pancreatic carcinoma, these neoplasms can arise either sporadically or in familial clusters. Extensive chromosome abnormalities are frequent, as is loss of heterozygosity at loci known to contain the tumor suppressor genes DCC, p53, and MTS1. Although the genetic examination of all pancreatic cancers is important, the examination of familial cases is especially useful in that these allow the identification of uniform genetic alterations that are inherited through the germ line. Much additional work needs to be done before the genetic basis of pancreatic cancer is completely understood. Although our knowledge is limited, it is clear that genetic analyses can be used to establish the prognosis for a patient with pancreatic cancer and, it is hoped, will someday be used in the management, treatment, and detection of pancreatic cancer.

Congenital anomalies and genetic disorders in families of children with central nervous system tumours

Medical genetic histories of 165 children with primary central nervous system (CNS) tumours and 4599 relatives of these probands were examined to identify birth defects or genetic disorders that may be associated with the aetiology of CNS tumours. Twelve primary malignancies were found in 329 (4%) of the parents of probands. Two of 99 half sibs but no full sibs had malignancies. Twenty-four percent of families had histories warranting consultation for an inherited disorder or birth defect. Single instances of malformations or genetic disorders were reported in 36 families and several disorders were reported in more than one family, including familial hypercholesterolaemia (4), olivopontocerebellar atrophy (2), and familial abdominal aortic aneurysm (2). Although recurring abnormalities were not identified in probands, it is possible that one or more of the birth defects or genetic disorders observed in probands or relatives may be associated with CNS tumourigenesis.

Molecular, cytogenetic, and phenotypic studies of a constitutional reciprocal translocation t(5;10)(q22;q25) responsible for familial adenomatous polyposis in a Dutch pedigree

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 to 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.

Adenomatous polyposis coli and a cytogenetic deletion of chromosome 5 resulting from a maternal intrachromosomal insertion

We present the clinical and laboratory findings in an institutionalised adult patient originally referred for autism. A high risk of colorectal cancer was predicted when an interstitial deletion of the long arm of chromosome 5, del(5)(q15q22.3), was detected in her lymphocytes and deletion of the MCC and APC genes confirmed by molecular analysis. Adenomatous polyposis coli and carcinoma of the rectum were subsequently diagnosed in the patient. She was profoundly mentally retarded, autistic, and had minor dysmorphic features consistent with those of previous patients with similar deletions. The deletion arose as a result of recombination within the small insertion loop formed at meiosis by the direct insertion (dir ins(5)(q22.3q14.2q15)) found in the patient's mother. This family further confirms the cytogenetic mapping of both MCC and APC genes to 5q22 and comparison with other recent cases suggests that both genes and their closely linked markers lie within the 5q22.1 subband.

Evaluation of molecular genetic diagnosis in the management of familial adenomatous polyposis coli: a population based study

A population based clinical and molecular genetic study of familial adenomatous polyposis coli (FAPC) was performed to investigate the value of molecular genetic analysis and ophthalmological assessment in the presymptomatic diagnosis of FAPC. The point prevalence of affected patients was 2.62 x 10(-5) (1/38,000) and the minimum heterozygote prevalence was estimated at 3.8 x 10(-5) (1/26,000). Eight of 33 (24%) probands were new mutations. Forty-eight asymptomatic relatives at 50% prior risk aged between 10 and 40 years were assessed for risk modification with linked DNA markers: in nine subjects (18%) the family structure was unsuitable for linkage based analysis, but 32 subjects were informative with a panel of intragenic and closely linked markers (25 had a combined age/DNA related risk of < 1% (low risk group) and seven were at high risk (DNA predicted risk > 99%)). Ophthalmological assessment for CHRPEs showed that 27/43 (63%) affected patients and high risk relatives and 0/18 low risk relatives had more than three CHRPEs. Interfamilial variation in CHRPE expression was apparent. This study has shown that DNA based risk modification with intragenic and closely linked DNA markers is informative in most FAPC families. In addition to the clinical benefits of presymptomatic diagnosis for FAPC, the reduction in screening for low risk relatives (365 person years in the present study) means that molecular genetic diagnosis of FAPC is a cost effective procedure.

Two cases of 5q deletions in patients with familial adenomatous polyposis: possible link with Caroli's disease

Two cases are reported of patients with deletions of chromosome 5q. Both have familial adenomatous polyposis (FAP) and mild mental retardation. In both, macroscopic polyposis was confined to the proximal colon in adult life (in their thirties) although microscopic adenomatosis was shown in the more distal colon with occasional single polyps. Both subjects had dermoid cysts, and congenital hypertrophy of the retinal pigment epithelium (CHRPE) was seen in case 2. Case 1 has gastroduodenal polyps and desmoid tumours; case 2 has a marfanoid habitus with an abnormal pectus, wasted calf muscles and clawing of the toes, and Caroli's syndrome. His deletion is cytogenetically more extensive than that in case 1. The paucity of adenomas in the left side of the colon suggests that FAP cannot always confidently be excluded by sigmoidoscopy alone. The expression of the disease in the colon in these cases could be milder than in the more usual autosomal dominant cases where nonsense mutations resulting from single base changes of small deletions rather than deletion of the whole gene are the usual finding.

Tumour suppressor genes and colorectal neoplasia

Two distinct gene classes have been implicated in colorectal carcinogenesis. Tumour promoter genes (oncogenes, dominant oncogenes) produce an excessive positive stimulus to cell proliferation. The ras family of oncogenes are an example. Acquired mutations of the c-k-ras gene are commonly found in colonic adenomas and carcinomas. Tumour suppressor genes (anti-oncogenes, recessive oncogenes) normally constrain or regulate cell proliferation. Loss of this function through gene deletion or mutation is oncogenic. Inherited tumour suppressor gene mutations have now been identified in several of the familial cancer syndromes. Acquired tumour suppressor gene mutations are found in both sporadic and hereditary cancers. Together with the tumour promoter genes they provide the genetic basis for the cellular changes occurring during carcinogenesis. The retinoblastoma gene was the first human tumour suppressor gene to be characterized and exemplifies the class. More recently, linkage studies in the hereditary cancer syndromes and the detection of specific deletions in sporadic tumours have helped to identify several new tumour suppressor genes. At least four of these (MCC, APC, p53 and DCC) apparently contribute to sporadic colorectal carcinogenesis. Germ line APC mutations produce the inherited colorectal cancer syndrome familial adenomatous polyposis (FAP). Detection of these mutations using linked markers has already found clinical application in the screening of families with this disease. In the future, genetic diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) and the recognition of those genetically susceptible to sporadic colorectal cancer may become possible. At the same time, as our understanding of the genes involved improves, new avenues for treatment and prevention of colorectal cancer may emerge.

Yeast artificial chromosomes for the molecular analysis of the familial polyposis APC gene region

Two yeast artificial chromosomes (YACs) spanning a total distance of 1.1 megabase pairs of DNA around the MCC (for mutated in colorectal carcinoma) and APC (for adenomatous polyposis coli) genes at 5q21 have been isolated and characterized. Starting from the MCC gene, a strategy was undertaken to identify constitutional submicroscopic deletions in familial adenomatous polyposis patients that might considerably narrow down the position of the APC gene. To this end, YACs identified by the MCC gene were screened across a chromosome 5-specific cosmid library to provide a source of DNA probes for genomic scanning. The cosmids isolated from these experiments were used to screen a panel of somatic cell hybrids containing chromosome 5 segregated from patients suspected to carry putative interstitial deletions. This screening approach led to the confirmation of a small heterozygous deletion in a polyposis patient that overlaps one of the two isolated YACs. This YAC has been shown to contain the entire APC gene, in addition to a significant portion of DNA flanking the 5' end of the gene, and should therefore prove a valuable resource for functional studies by transfer to colorectal tumor-derived cell lines.

Constitutional balanced translocations in patients with solid tumors

In a sample of 329 patients with a solid tumor (colon and breast adenocarcinoma, cervical carcinoma, and meningioma), four balanced constitutional translocations were observed. Two were t(13q14q), and two were reciprocal translocations. Comparison with surveys of newborns showed a significant excess of translocations in our sample.

Phenotypic, cytogenetic, and molecular studies of three patients with constitutional deletions of chromosome 5 in the region of the gene for familial adenomatous polyposis

We have studied three patients, one with extensive polyposis of the colon, who have constitutional interstitial deletions of the long arm of chromosome 5. High-resolution banding studies indicated that the deletion in the patient with polyposis spans the region 5q21-q22, which includes APC, a gene involved in familial adenomatous polyposis and sporadic colon cancer. Molecular analysis with probes for sequences flanking APC confirmed this conclusion. The deletions in the other two patients, who are too young to have developed polyposis, had breakpoints within this region, precluding the use of cytogenetic analysis alone in making definitive predictions about their risks. Molecular studies resolved the uncertainty; in situ and quantitative Southern hybridizations of four probes for polymorphic segments revealed that one of the patients has a deletion of MCC, a gene which is approximately 150 kb proximal to APC, and two flanking markers. He is at increased risk for polyposis, while the other patient is not. The physical descriptions of these patients, in conjunction with cases in the literature, begin to allow delineation of two distinct 5q-syndromes. These studies also provide precise physical mapping data for D5S71, D5S81, D5S84, and MCC on 5q.

An intrachromosomal insertion causing 5q22 deletion and familial adenomatous polyposis coli in two generations

We report familial adenomatous polyposis coli (FAPC) with epidermoid cysts, osteomata, and areas of congenital hypertrophy of the retinal pigment epithelium (CHRPEs) in a male patient and his maternal aunt, both of whom suffered a mild to moderate degree of mental handicap. Both had an interstitial deletion of the long arm of chromosome 5 (del(5)(q22q23.2)). Two other normal family members had the underlying direct insertion of chromosome 5(dir ins(5)(q31.3q22q23.2)). Molecular genetic and fluorescent hybridisation studies have shown that loci D5S37 and D5S98 are outside the deletion whereas loci detected by probes EF5.44 and YN5.48 are lost. As expected, the molecular analyses indicate loss of one allele at the MCC and APC loci. The APC gene is located within band 5q22. Familial direct insertions should be considered as a cause of recurrent microdeletion syndromes.

Coping styles, psychopathology and intellectual performance in patients with familial adenomatous polyposis

Thirty-eight patients with familial adenomatous polyposis (FAP) were compared with 19 patients with ulcerative colitis (UC) for differences in illness-related variables, coping styles, psychiatric symptomatology, and intellectual performance. Patients with FAP had significantly less education, longer time since recent surgery, less psychiatric illness, and evidence of less preoccupation with their illness, as compared with UC patients. FAP patients with a positive family history (N = 28) scored significantly lower on both verbal and performance intellectual tests, even when taking education into account, compared with FAP patients without a family history (N = 9). The relevance of these findings to the ongoing monitoring and surveillance of patients with FAP is discussed.

Gardner syndrome in a boy with interstitial deletion of the long arm of chromosome 5

We described a 15-year-old boy with Gardner syndrome (GS), mental retardation, and craniofacial abnormalities. High-resolution banding analysis showed an interstitial deletion of the long arm of chromosome 5 (q22.1----q31.1). The breakpoints in the present case and in 3 previously reported 5q- patients with adenomatous polyposis coli suggest that the gene responsible for GS/or familial polyposis coli (FPC) is in the 5q22 region, a result consistent with the findings of linkage studies.

Lower motor neuron degeneration and familial predisposition to colonic neoplasia in two adult siblings

A previously unreported association between a familial predisposition to colonic neoplasia and familial adult onset lower motor neuron (LMN) degeneration is reported. Two brothers presented at the ages of 53 and 44 years with multiple colonic adenomata and invasive colonic carcinoma respectively. Subsequently both developed a virtually identical pattern of motor neuron disease of progressive muscular atrophy type. At presentation both had LMN weakness affecting predominantly the upper limb and neck muscles. The disease progressed rapidly to involve the lower limb and bulbar musculature and both brothers died after a 15 month course. Necropsy was performed on one brother and showed pathological changes confined to the LMNs with no evidence of involvement of the pyramidal tracts or motor cortex. The combination of these diseases in two brothers may be of importance in the search for genes responsible for familial motor neuron disorders. It is suggested that a genomic search should be directed initially to the vicinity of known colon neoplasia genes, particularly 5q, 17q and 18q.

Characterization and mapping of microdissected genomic clones from the adenomatous polyposis coli (APC) region

The gene associated with adenomatous polyposis coli (APC) has been mapped to the long arm of chromosome 5. To saturate the APC region with DNA markers, two independent microdissection libraries with an emphasis on 5q21.2-21.3 and 5q22 have been constructed from GTG-banded human metaphase chromosomes. PCR-amplified insert DNA of the primary amplificate used as a probe in chromosomal in situ suppression (CISS) hybridization of human metaphase spreads revealed region-specific signals at the chromosomal site that was excised for cloning. One hundred forty-two inserts, derived from both libraries, have been characterized in more detail. Deletion mapping analysis was performed with 17 single-copy clones on a hamster-human hybrid cell panel. Seven of these clones were located within two interstitial deletions of 6-8 Mb from APC-affected individuals around chromosome bands 5q21-22. The identification of new microclones mapping into these deletions and their use in isolating YAC clones should contribute to the construction of a contiguous physical map of the APC region.

Fine mapping of probes in the adenomatous polyposis coli region of chromosome 5 by in situ hybridization

The gene for adenomatous polyposis coli has been localized to 5q21-22. We have mapped six probes from this region using isotopic or nonisotopic in situ hybridization. Using tritium-labeled probes we localized II227 (D5S37) to 5q14-15 and ECB27 (D5S98) to 5q21. Following hybridization with biotin-labeled probes, the positions of signals along the chromosomes were measured as fractional length relative to the length of the chromosome arm from centromere to qter (FLcen-qter). Ninety-five percent confidence limits, compared with standard karyotypes, provided the corresponding band localization. By this method we localized Cllpll (D5S71) to FLcen-qter 0.407-0.452 (5q21.1-21.3), ECB27 to FLcen-qter 0.426-0.473 (5q21.3), YN5.48 (D5S81) to FLcen-qter 0.459-0.496 (5q21.3-22.2), and ECB134 (D5S97) to FLcen-qter 0.509-0.533 (5q22.3-23.1). ECB220 had three sites of hybridization, a major site at FLcen-qter 0.460-0.492 (5q21.3-22.1) and minor sites at FLcen-qter 0.299-0.339 (5q14.3-15) and FLcen-qter 0.629-0.691 (5q23.3-31.2). We have shown that the chromosome 5 breakpoint in a t(5;15) translocation from a patient with Gardner's syndrome (GM03314) is between Cllpll and ECB27. Linkage data are presented suggesting that ECB27 is located on the same side of the APC locus as II227. These and published results including data on several constitutional deletions (M, SD, and brothers PW and ND) give a probable order of [cen] - [II227, proximal SD breakpoint] - [Cllpll] - [proximal PW/ND, M breakpoint(s), GM03314 breakpoint] - [ECB27] - [APC] - [YN5.48] - [distal PW/ND breakpoint] - [ECB134] - [distal M breakpoint] - [qter]. The major site of ECB220 appears to be between ECB27 and the distal PW/ND breakpoint; the distal SD breakpoint is distal to YN5.48.

Ionizing radiation and genetic risks. I. Epidemiological, population genetic, biochemical and molecular aspects of Mendelian diseases

This paper reviews the currently available information on naturally occurring Mendelian diseases in man; it is aimed at providing a background and framework for discussion of experimental data on radiation-induced mutations (papers II and III) and for the estimation of the risk of Mendelian disease in human populations exposed to ionizing radiation (paper IV). Current consensus estimates indicate that a total of about 125 per 10(4) livebirths are directly affected by one or another naturally occurring Mendelian disease (autosomal dominants, 95/10(4); X-linked ones, 5/10(4); and autosomal recessives, 25/10(4). These estimates are conservative and take into account conditions which are very rare and for which prevalence estimates are unavailable. Most, although not all, of the recognized "common" dominants have onset in adult ages while most sex-linked and autosomal recessives have onset at birth or in childhood. Autosomal dominant and X-linked diseases (i.e., the responsible mutant alleles) presumed to be maintained in the population due to a balance between mutation and selection are the ones which may be expected to increase in frequency as a result of radiation exposures. Viewed from this standpoint, the above assumption seems safe only for a small proportion of such diseases; for the remainder, there is no easy way to discriminate between different mechanisms that may be responsible or to rigorously exclude some in favor of some others. Mutations in genes that code for enzymic proteins are more often recessive in contrast to those that code for non-enzymic proteins, which are more often dominant. At the molecular level, with recessives, a wide variety of changes is possible and these include specific types of point mutations, small and large intragenic deletions, multilocus deletions and rearrangements. In the case of dominants, however, the kinds of recoverable point mutations and deletion-type changes are less extensive because of functional constraints. The mutational potential of genes varies, depending on the gene, its size, sequence content and arrangement, location and its normal functions, and can be grouped into three groups: those in which only point mutations have been found to occur, those in which only deletions or other gross changes have been recovered and those in which both kinds of changes are known. Molecular data are available for about 75 Mendelian conditions and these suggest that in approximately 50% of them, the changes categorized to date are point mutations and in the remainder, intragenic deletions or other gross changes; there does not seem to be any fundamental difference between dominants and recessives with respect to the underlying molecular defect.(ABSTRACT TRUNCATED AT 400 WORDS)

Double chromosome anomaly: interstitial deletion 5q and reciprocal translocation (1;11)(p22;q21)

We describe a girl with multiple congenital abnormalities and developmental delay; her karyotype showed an apparently balanced translocation between the short arm of chromosome 1 and the long arm of chromosome 11, and an interstitial deletion of the long arm of chromosome 5 (q15q31). The clinical findings are compared with those described in other cases of 5q deletion, and the origin of the chromosome rearrangements is briefly discussed.

A constitutional 5q23 deletion

A 14 month old girl was found to have a deletion of the whole of band 5q23. By comparing 19 other cases monosomic for a part of the 5q13-q31 segment, the constitutional 5q interstitial deletions fall into two groups: adult patients with Gardner-like symptoms and mental retardation associated with deletion 5q21-q22, and patients (mostly children) with unspecific signs and symptoms and different deletions.

CpG island clones from a deletion encompassing the gene for adenomatous polyposis coli

Adenomatous polyposis coli (APC), a dominantly inherited disorder, has been mapped to chromosome 5q15-q21 by family linkage studies. Cells from patients with deletions in this region, in one case associated with polyposis in a family, have been used to construct human hamster hybrid cell lines that retain either the normal or deleted chromosome 5. These lines have been used to identify markers from the region of the polyposis gene obtained by cloning the ends of 0.5- to 2-megabase BssHII fragments purified by pulsed-field gel electrophoresis. Three markers are described that map within the deletions and must therefore be close to the APC gene.

Interstitial deletion, del(4)(q33q35.1), in a mother and two children

The inheritance of autosomal deletions from affected parents has only rarely been reported. We report an unbalanced interstitial deletion, del(4)(q33q35.1), in a mother and two male offspring. The mother and older sib are mentally retarded but have only mild dysmorphic features. The younger sib, at five months, is showing signs of developmental delay. All three patients show some abnormalities in common with cases that have terminal deletions of 4q with breakpoints at 4q33, but in general exhibit less severe abnormalities. The family illustrates the importance of detailed cytogenetic analysis of children with developmental delay who do not display major dysmorphic features.