The transCampus Metabolic Training Programme Explores the Link of SARS-CoV-2 Virus to Metabolic Disease

Currently, we are experiencing a true pandemic of a communicable disease by the virus SARS-CoV-2 holding the whole world firmly in its grasp. Amazingly and unfortunately, this virus uses a metabolic and endocrine pathway via ACE2 to enter our cells causing damage and disease. Our international research training programme funded by the German Research Foundation has a clear mission to train the best students wherever they may come from to learn to tackle the enormous challenges of diabetes and its complications for our society. A modern training programme in diabetes and metabolism does not only involve a thorough understanding of classical physiology, biology and clinical diabetology but has to bring together an interdisciplinary team. With the arrival of the coronavirus pandemic, this prestigious and unique metabolic training programme is facing new challenges but also new opportunities. The consortium of the training programme has recognized early on the need for a guidance and for practical recommendations to cope with the COVID-19 pandemic for the community of patients with metabolic disease, obesity and diabetes. This involves the optimal management from surgical obesity programmes to medications and insulin replacement. We also established a global registry analyzing the dimension and role of metabolic disease including new onset diabetes potentially triggered by the virus. We have involved experts of infectious disease and virology to our faculty with this metabolic training programme to offer the full breadth and scope of expertise needed to meet these scientific challenges. We have all learned that this pandemic does not respect or heed any national borders and that we have to work together as a global community. We believe that this transCampus metabolic training programme provides a prime example how an international team of established experts in the field of metabolism can work together with students from all over the world to address a new pandemic.

Assessment of the genetic causes of recessive childhood non-syndromic deafness in the UK - implications for genetic testing

Approximately one in 2000 children is born with a genetic hearing impairment, mostly inherited as a non-syndromic, autosomal recessive trait, for which more than 30 different genes have been identified. Previous studies have shown that one of these genes, connexin 26 (GJB2), accounts for 30-60% of such deafness, but the relative contribution of the many other genes is not known, especially in the outbred UK population. This lack of knowledge hampers the development of diagnostic genetic services for deafness. In an effort to determine the molecular aetiology of deafness in the population, 142 sib pairs with early-onset, non-syndromic hearing impairment were recruited. Those in whom deafness could not be attributed to GJB2 mutations were investigated further for other mapped genes. The genetic basis of 55 cases (38.7%) was established, 33.1% being due to mutations in the GJB2 gene and 3.5% due to mutations in SLC26A4. None of the remaining 26 loci investigated made a significant contribution to deafness in a Caucasian population. We suggest that screening the GJB2 and SLC26A4 genes should form the basis of any genetic testing programme for childhood deafness and highlight a number of important issues for consideration and future work.

Functional MASP2 single nucleotide polymorphism plays no role in psoriasis

BACKGROUND

Psoriasis is a heritable disease and genome-wide scans have implicated several loci of susceptibility. The gene for MASP-2, a protease involved in complement activation, is located within one of these loci on chromosome 1p.

OBJECTIVES

To assess whether partial or total MASP-2 deficiency is a risk factor for developing psoriasis.

METHODS

We screened a cohort of patients affected by plaque psoriasis and their parents by restriction fragment length polymorphism analyses.

RESULTS

We detected a single nucleotide polymorphism that leads to an amino acid exchange, which results in dissociation of MASP-2 from a carbohydrate recognition complex.

CONCLUSIONS

We show that this mutant allele is not associated with psoriasis. There was no favoured transmission from parents to affected offspring. The calculated allele frequency in this psoriasis group (Scottish and English) was 0.0326, and in the unaffected group 0.0379.

Molecular heterogeneity in two families with auditory pigmentary syndromes: the role of neuroimaging and genetic analysis in deafness

We report two cases in which the probands presented with deafness and a family history of a dominantly inherited auditory pigmentary syndrome, yet the cause of deafness in each proband was not associated with the pigmentary abnormalities but was a result of mutations in SLC26A4, the gene mutated in Pendred's syndrome. The first case is a young woman with congenital sensorineural hearing loss and a family history of piebaldism. Despite showing no pigmentary abnormalities, the proband was found to harbor the same KIT mutation as her relatives affected by piebaldism, as well as two mutations in the SLC26A4 gene. In the second case, 2-year-old identical twin boys born to deaf parents presented with congenital sensorineural deafness and an extensive maternal family history of Waardenburg's syndrome type I (WSI). Their father had recessively inherited deafness associated with dilated vestibular aqueducts and a clinical diagnosis of Pendred's syndrome was made in him, which was confirmed molecularly. As the twin boys did not have features of WSI, both the mother and children were tested for mutations in SLC26A4 which showed the mother to be a carrier of a single mutation and both boys to be compound heterozygotes, illustrating pseudodominant inheritance of the condition.

Multiple endocrine neoplasia type 1 (MEN1) germline mutations in familial isolated primary hyperparathyroidism

BACKGROUND

Familial isolated hyperparathyroidism (FIHP) is an autosomal dominant disorder characterized by uniglandular or multiglandular parathyroid tumours that occur in the absence of other endocrine tumours. The disorder may represent either an early stage of multiple endocrine neoplasia type 1 (MEN1), or an allelic variant of MEN1, or a distinct entity involving another locus. We have explored these possibilities in seven families in whom primary hyperparathyroidism occurred as the sole endocrinopathy.

METHODS

Seven FIHP families were ascertained and venous blood samples obtained from 35 members (17 affected and 18 unaffected) for DNA sequence analysis of the MEN1 gene. The mean (+/- SD) follow-up period in the 17 affected members was 15.06 (+/- 8.83) years.

RESULTS

Four heterozygous germline mutations of the MEN1 gene were identified. These consisted of two 4-bp intragenic deletions that would result in prematurely truncated proteins, and two missense (Asp153Val and Ala411Pro) mutations. Furthermore, analysis of parathyroid tumour DNA from one individual revealed a loss of the wild-type allele and retention of the mutant allele, consistent with Knudson's 'two-hit' model of hereditary cancer and a tumour suppressor role for MEN1 in FIHP.

CONCLUSIONS

Our results provide further support for FIHP being a distinct allelic variant of MEN1, and an analysis of the 16 mutations reported to date indicate that FIHP is associated with a higher frequency of missense MEN1 mutations.

Pulmonary arterial hypertension and type-I glycogen-storage disease: the serotonin hypothesis

A case of pulmonary arterial hypertension in a patient with type-Ia glycogen-storage disease, a rare autosomal recessive disorder caused by a deficiency of glucose-6-phosphatase is reported in this study. It has been suggested that the occurrence of pulmonary arterial hypertension in type-Ia glycogen-storage disease could be due to an abnormal production of vasoconstrictive amines such as serotonin. To test this hypothesis, plasma serotonin concentrations were prospectively measured in 13 patients with type-Ia glycogen-storage disease, one patient with severe pulmonary hypertension and type-Ia glycogen-storage disease, 16 patients displaying severe pulmonary arterial hypertension, and 26 normal healthy controls. Elevated plasma serotonin concentrations were found in patients with either severe pulmonary arterial hypertension (38.8+/-7.3 nmol x L(-1)) or type-Ia glycogen-storage disease (36.8+/-11.5 nmol x L(-1)), as compared with controls (8.8+/-0.6 nmol x L(-1), p<0.001). Plasma serotonin was dramatically elevated in the patient with type-Ia glycogen-storage disease and pulmonary arterial hypertension (113.4 nmol x L(-1)). It is concluded that type-Ia glycogen-storage disease may be another condition in which abnormal handling of serotonin is one event in a multistep process leading to severe pulmonary arterial hypertension.

Corneodesmosin expression in psoriasis vulgaris differs from normal skin and other inflammatory skin disorders

SUMMARY

Corneodesmosin (Cdsn) is a late differentiation epidermal glycoprotein putatively involved in keratinocyte adhesion. The Cdsn gene lies within the susceptibility region on chromosome 6p21.3 (PSORS1) for psoriasis, a common chronic disfiguring skin disease. A particular allelic variant of Cdsn has a strong association with psoriasis. Therefore, genetically and biologically, Cdsn is a possible candidate gene for psoriasis susceptibility. To investigate a potential role for Cdsn in psoriasis pathogenesis, protein expression studies were performed by quantitative immunohistochemistry on normal skin, psoriatic skin (lesional and nonlesional), and other skin disorders using monoclonal antibodies (G36-19 and F28-27). In normal and nonlesional skin, Cdsn was expressed in stratum corneum and one or two layers of superficial stratum granulosum. In lesional psoriasis, there was a significant increase in Cdsn expression, which was observed in multiple layers of stratum spinosum and in stratum corneum. The expression pattern varied from granular, cytoplasmic immunoreactivity to cell surface labeling with weakly immunoreactive cytoplasm. In chronic atopic dermatitis, lichen planus, mycosis fungoides, and pityriasis rubra pilaris, Cdsn immunoreactivity was confined to stratum corneum and upper stratum granulosum with no stratum spinosum immunoreactivity. Immunoelectron microscopy of normal and lesional psoriatic skin demonstrated Cdsn release concomitant with involucrin incorporation into cell envelopes and completed before mature envelope formation. Extracellular release of Cdsn occurred at a lower level of the epidermis in psoriasis than normal skin. These protein expression studies provide evidence of altered Cdsn expression in psoriasis consistent with a role of Cdsn in disease pathogenesis. Further functional and genetic studies of Cdsn are justified to determine its role as a potential psoriasis-susceptibility factor.

Enlarged vestibular aqueduct: a radiological marker of pendred syndrome, and mutation of the PDS gene

Although the textbook view of Pendred syndrome is that of an autosomal recessive condition characterized by deafness and goitre, it is increasingly clear that not all such patients present this classical clinical picture. Malformations of the inner ear, specifically enlargement of the vestibular aqueduct, are common in Pendred syndrome and mutations in the PDS (Pendred Syndrome) gene have been recorded in patients presenting with deafness and vestibular aqueduct dilatation only, without other features of Pendred syndrome. Since this is the most common radiological malformation of the cochlea in deaf patients, we investigated what proportion of such cases were due to mutation of the PDS gene. We assessed 57 patients referred with radiological evidence of vestibular aqueduct enlargement, by history, clinical examination, perchlorate discharge test and molecular analysis of the PDS locus. Forty-one patients (72%) had unequivocal evidence of Pendred syndrome. The finding of a single heterozygous mutation at the PDS gene in a further eight was strongly suggestive of a critical role for pendrin, the protein product of the PDS gene, in the generation of enlarged vestibular aqueducts in at least 86% (49/57 cases) of patients with this radiological malformation. Securing the diagnosis of Pendred syndrome may be difficult, especially in the single case. Goitre is an inconstant finding, and the perchlorate discharge test, although helpful, is of diagnostic value only if abnormal. Enlargement of the vestibular aqueduct should be considered as the most likely presentation of Pendred syndrome and should prompt specific investigation of that diagnostic possibility. Pendred syndrome might henceforth be recharacterized as deafness with enlargement of the vestibular aqueduct, which is sometimes associated with goitre.

Concurrence of Pendred syndrome, autoimmune thyroiditis, and simple goiter in one family

Pendred syndrome is the autosomal recessively transmitted association of familial goiter and congenital deafness. There is no specific biochemical marker of this disease, and the diagnosis depends upon the demonstration of the triad of congenital sensorineural hearing loss, goiter, and abnormal perchlorate discharge test. Pendred syndrome is caused by mutations within the putative ion transporter gene (PDS gene), located on chromosome 7q. A wide variation in the clinical presentation of this condition, and its well documented phenotypic overlap with other thyroid disorders (such as Hashimoto's thyroiditis), can lead to diagnostic difficulties. The potential for misdiagnosis increases when these disorders occur coincidentally in the same family. We describe a kindred in which Pendred syndrome, autoimmune thyroiditis, and simple goiter coexisted, to highlight these diagnostic pitfalls and to illustrate the use of mutational analysis in resolving diagnostic confusion.

Prevalence, age of onset, and natural history of thyroid disease in Pendred syndrome

BACKGROUND

We have sought to establish the prevalence of goitre within a Pendred syndrome (PS) cohort and to document the course of thyroid disease in this patient group. As part of a genetic study of PS we have assessed 57 subjects by perchlorate discharge test and in 52 (M 21, F 31, age range 9-54 years) a discharge of radioiodide of >10% was observed.

RESULTS

Goitre was present in 43 (83%) of the cohort (28 F, 15 M), generally developing after the age of 10 years, 56% remained euthyroid (age range 9-37 years), and 19 patients (44%) had objective evidence of hypothyroidism, all of whom had goitre.

CONCLUSIONS

In summary, thyroid dysfunction in PS is variable and inclusion of goitre as a diagnostic requirement will maintain significant underascertainment. The recent identification of the genetic defect underlying PS is likely to provide an important diagnostic aid in the identification of this disorder and this communication should assist clinicians in identifying deaf patients who ought to be considered for this investigation.

Identification of two different mutations in the PDS gene in an inbred family with Pendred syndrome

Recently the gene responsible for Pendred syndrome (PDS) was isolated and several mutations in the PDS gene have been identified in Pendred patients. Here we report the occurrence of two different PDS mutations in an extended inbred Turkish family. The majority of patients in this family are homozygous for a splice site mutation (1143-2A-->G) affecting the 3' splice site consensus sequence of intron 7. However, two affected sibs with non-consanguineous parents are compound heterozygotes for the splice site mutation and a missense mutation (1558T-->G), substituting an evolutionarily conserved amino acid. The latter mutation has been found previously in two Pendred families originating from The Netherlands, indicating that the 1558T-->G mutation may be a common mutation.

Ultraviolet B induced suppression of induction of contact sensitivity in human skin is not associated with tumour necrosis factor-alpha-308 or interleukin-10 genetic polymorphisms

Low doses of ultraviolet B (UVB) can induce localized immunosuppression in skin. This effect may be important in the induction of skin cancers and is thought to be mediated by tumour necrosis factor (TNF) alpha and interleukin (IL) 10 in conjunction with other factors. In humans a transition polymorphism in the TNF-alpha gene may affect TNF-alpha secretion and the promoter region of the IL-10 gene contains a CA repeat polymorphism which may affect gene function. We have therefore investigated the association of these polymorphisms with UVB-induced immunosuppression in humans. Volunteers (n = 42) were irradiated with UVB then sensitized on irradiated skin with diphenylcyclopropanone (DPCP) and subsequently antigen challenged with DPCP. DNA was extracted from blood samples and volunteers genotyped for the TNF-alpha polymorphism by polymerase chain reaction (PCR) and restriction digestion. The CA repeat polymorphism was amplified by PCR and sized by gel electrophoresis. Twenty-four volunteers were susceptible to UVB-induced immunosuppression and 18 were resistant. The association of allele frequencies and phenotype was statistically tested using a chi2-test. For both the TNF-alpha and IL-10 polymorphisms, there was no statistically significant association between allele types and response to UVB. These results indicate that variation in the immune response to UVB in humans is not associated with the TNF-alpha-308 transition or IL-10 CA repeat polymorphisms, although other as yet undetected DNA sequence variants of these genes may be involved.

Genomic structure of the human congenital chloride diarrhea (CLD) gene

Congenital chloride diarrhea (CLD) is caused by mutations in a gene which encodes an intestinal anion transporter. We report here the complete genomic organization of the human CLD gene which spans approximately 39kb, and comprises 21 exons. All exon/intron boundaries conform to the GT/AG rule. An analysis of the putative promoter region sequence shows a putative TATA box and predicts multiple transcription factor binding sites. The genomic structure was determined using DNA from several sources including multiple large-insert libaries and genomic DNA from Finnish CLD patients and controls. Exon-specific primers developed in this study will facilitate mutation screening studies of patients with the disease. Genomic sequencing of a BAC clone H_RG364P16 revealed the presence of another, highly homologous gene 3' of the CLD gene, with a similar genomic structure, recently identified as the Pendred syndrome gene (PDS).

Lack of hemizygosity for the insulin-like growth factor I receptor gene in a quantitative study of 33 Silver Russell syndrome probands and their families

Previous studies have shown that individuals with a deletion of 15q26.1-->qter, which includes the insulin-like growth factor I receptor (IGFIR) gene, may exhibit phenotypic characteristics similar to those individuals with Silver-Russell Syndrome (SRS). Thirty-three SRS probands, with normal karyotypes, and their parents were investigated for the presence of both copies of IGFIR by gene dosage analysis of Southern blot hybridisation. All 33 SRS probands have both copies of IGFIR. Tetranucleotide repeat marker analysis for three locations on 15q also ruled out other deletions in these regions for those markers that were informative. Two important functional regions of IGFIR were also investigated for DNA mutations, using single-stranded conformational polymorphism analysis. No mutations were found in the cysteine-rich region involved in ligand binding (exon 3) or the ATP binding region (exon 16) which could contribute to the SRS phenotype. However, a silent mutation in the third position of one of the codons in the ATP region (3174G-->A, 1013 Glu-->Glu) was found.

Pendred syndrome--100 years of underascertainment?

Pendred syndrome is an autosomal recessive condition classically characterized by deafness and goitre. Since both cochlear and thyroid pathology are required to secure the diagnosis, it is unclear whether the condition might present without the classical features. The perchlorate discharge test, the gold-standard investigation for Pendred syndrome, is non-specific, and in the absence of alternative means of confirming the diagnosis, its sensitivity is unknown. We used the recent mapping of the gene to chromosome 7q to identify pedigrees with a likely diagnosis of Pendred syndrome, and assessed the prevalence of clinical parameters of disease in affected patients. Thirty-six familial cases showed co-segregation between disease and the Pendred syndrome locus on chromosome 7q. Clinical and investigative findings were compared in index cases (n = 18) vs. affected siblings (n = 18). The overall prevalence of goitre was 73%, higher in index cases (94%) than in siblings (56%), many of whom had not previously been considered to have the condition. One perchlorate discharge test was false-negative (2.9%). Radiological malformations of the cochlea were identified in 86% of cases. Securing a diagnosis of Pendred syndrome may be difficult, especially in the single case. The perchlorate discharge test, although valuable, is difficult to undertake in the younger patient, and radiology may assist in diagnosing such patients.

Pendred syndrome: evidence for genetic homogeneity and further refinement of linkage

Pendred syndrome is the association between congenital sensorineural deafness and goitre. The disorder is characterised by the incomplete discharge of radioiodide from a primed thyroid following perchlorate challenge. However, the molecular basis of the association between hearing loss and a defect in organification of iodide remains unclear. Pendred syndrome is inherited as an autosomal recessive trait and has recently been mapped to 7q31 coincident with the non-syndromic deafness locus DFNB4. To define the critical linkage interval for Pendred syndrome we have studied five kindreds, each with members affected by Pendred syndrome. All families support linkage to the chromosome 7 region, defined by the microsatellite markers D7S501-D7S523. Detailed haplotype analysis refines the Pendred syndrome linkage interval to a region flanked by the marker loci D7S501 and D7S525, separated by a genetic distance estimated to be 2.5 cM. As potential candidate genes have as yet not been mapped to this interval, these data will contribute to a positional cloning approach for the identification of the Pendred syndrome gene.

Identification of 17 mutations in ten exons in the COL4A5 collagen gene, but no mutations found in four exons in COL4A6: a study of 250 patients with hematuria and suspected of having Alport syndrome

Conditions for polymerase chain-reaction amplification of ten exon regions (Exons 3, 7, 11 through 13, and 15 through 19) of the collagen COL4A5 gene and four exon regions (Exons 2, and 12 through 14) of the COL4A6 gene were sequenced and established in this study. These Type IV collagen genes contain 51 and 48 exons, respectively. The sequences of these exons were determined in the two genes in 250 male patients with hematuria and suspected Alport syndrome. Seventeen mutations were found in nine of the ten exons studied in the COL4A5 gene in 17 patients, whereas no mutations were identified in COL4A6. One mutation was identical in two patients known to be unrelated. The results indicate that mutations in COL4A5 that leading to renal failure are more frequent than those involved in classic Alport syndrome, and also that mutations in COL4A6 are not likely to cause this disease. Furthermore, mutations in COL4A5 are distributed quite randomly and no "hot spots" were found.

Thyroid peroxidase: evidence for disease gene exclusion in Pendred's syndrome

OBJECTIVE

Pendred's syndrome is an association between congenital neurosensory deafness and goitre with abnormal discharge of iodide following perchlorate challenge, indicating a defect of iodide organification. Although Pendred's syndrome may cause up to 7.5% of all cases of congenital deafness, the molecular basis of the association between the hearing loss and the thyroid organification defect remains unknown. We chose to investigate the role of the thyroid peroxidase (TPO) gene as the genetic defect in Pendred's syndrome.

DESIGN

A highly informative variable number tandem repeat (VNTR), located 1.5 kb downstream of exon 10 of the TPO gene, was used to search for genetic linkage in multiple sibships affected by Pendred's syndrome.

PATIENTS

Seven kindreds were recruited from the UK, each with at least two affected members. We have also examined a large inbred Israeli family with two affected offspring and five unaffected children.

MEASUREMENTS

Individuals were assigned affected status based on the characteristic clinical features of Pendred's syndrome, namely the presence of congenital sensorineural hearing loss and the appearance in early life of a goitre. Additionally, at least one affected member from each sibship had a characteristic positive perchlorate discharge test (Morgans & Trotter, 1958). PCR amplification of genomic DNA at the TPO VNTR allowed assignment of genotypes to each individual and the calculation of a two-point LOD score.

RESULTS

In six of the nine sibships analysed we found obligatory recombination between TPO and Pendred's syndrome. Non-complementation observed in affected parents with an affected offspring excluded TPO in an affected sibship with genotype sharing and supports a hypothesis of genetic homogeneity for Pendred's syndrome. In two sibships, mutation of the TPO gene as the cause of Pendred's syndrome could not be excluded.

CONCLUSIONS

These data suggest that defects at the thyroid peroxidase locus on chromosome 2 are not the major cause of Pendred's syndrome.

Pendred syndrome (goitre and sensorineural hearing loss) maps to chromosome 7 in the region containing the nonsyndromic deafness gene DFNB4

Inherited causes account for about 50% of individuals presenting with childhood (prelingual) hearing loss, of which 70% are due to mutation in numerous single genes which impair auditory function alone (non-syndromic). The remainder are associated with other developmental anomalies termed syndromic deafness. Genes responsible for syndromic forms of hearing loss include the COL4A5 gene in Alport syndrome and the PAX3 and MITF genes in Waardenburg syndrome. Pendred syndrome is an autosomal recessive disorder associated with developmental abnormalities of the cochlea, sensorineural hearing loss and diffuse thyroid enlargement (goitre). Pendred syndrome is the most common syndromal form of deafness, yet the primary defect remains unknown. We have established a panel of 12 families with two or more affected individuals and used them to search for the location of the Pendred gene by linkage analysis. We excluded localization to four previously mapped nonsyndromic deafness loci but obtained conclusive evidence for linkage of the Pendred syndrome gene to microsatellite markers on chromosome 7q31 (D7S495 Zmax 7.32, Qmax = 0). This region contains a gene, DFNBL, for autosomal recessive non-syndromic sensorineural hearing loss. Multipoint analysis indicates that DFNB4 and Pendred syndrome co-localize to the same 5.5 centiMorgan (cM) interval flanked by D7S501 and D7S523. These data raise the possibility that Pendred syndrome is either allelic with DFNB4 or may represent an inherited contiguous gene disorder, not clinically manifest in the heterozygote.

Urticaria, arthralgia, and nephropathy without amyloidosis: another variant of the Muckle-Wells syndrome?

The term Muckle-Wells syndrome (MWS) describes an autosomal dominant disorder characterised by various combinations of urticaria, sensorineural deafness, amyloidosis, arthralgia and skeletal abnormalities. We describe a family with nephropathy and several symptoms of MWS, but no evidence of deafness or amyloidosis. Since nephropathy without amyloidosis has never been reported in MWS, but deafness is a feature of all reported pedigrees, we conclude that members of this family have a previously unreported inherited predisposition to urticaria, arthralgia and nephropathy which is distinct from the MWS phenotype.

Molecular genetic analysis of exons 1 to 6 of the APC gene in non-polyposis familial colorectal cancer

Familial adenomatous polyposis coli is caused by constitutional mutations in the APC gene. The hallmark of familial adenomatous polyposis coli is the presence of numerous (> 100) colorectal polyps, but mutations in the 5' end of the APC gene have been associated with familial colorectal cancer without florid polyposis. Although familial adenomatous polyposis coli accounts for only a minority of familial colorectal cancer cases, we hypothesised that APC mutations which were not associated with florid polyposis might make a significant contribution to nonpolyposis familial colorectal cancer. To investigate this possibility, we analysed 40 unrelated patients with familial colorectal cancer without classical familial adenomatous polyposis coli for mutations in exons 1 to 6 (codons 1 to 243) of the APC gene. No mutations were detected, but a C-->T polymorphism at nucleotide 333 (Arg-->Trp at codon 99) was identified. No 5' APC mutations were detected in two patients with desmoid tumours and a family history of colorectal cancer and polyps. We conclude that mutations in exons 1 to 6 of the APC gene are infrequent in patients with familial colorectal cancer who do not have many colorectal polyps.

DNA polymorphic haplotypes on the short arm of chromosome 11 and the inheritance of type I diabetes mellitus

The linked polymorphic loci 5' to the insulin gene and 3' to the c-Harvey-ras-1 (c-Ha-ras) gene, both localised to the short arm of chromosome 11, have been studied in 14 type I diabetic pedigrees. The use of a cloned gene probe corresponding to the polymorphic locus adjacent to the insulin gene, in combination with the restriction endonuclease PvuII, has permitted an improvement in the resolution of sizes of insert at this locus. An MspI restriction fragment length polymorphism at the c-Ha-ras proto-oncogene locus (4 cM upstream from the insulin gene) was used to identify parental insulin gene related alleles unambiguously, and subsequently a pedigree analysis was performed to determine whether subclasses of inserts at this locus track with insulin dependent diabetes. Segregation analysis demonstrated no linkage between the polymorphic loci 5' to the insulin gene, nor 3' to the c-Ha-ras, and type I diabetes. However, a similar analysis confirmed an association between the HLA locus chromosome 6 and insulin dependent diabetes.