Colorectal cancer (CRC) risk is well defined for families of patients with classical familial adenomatous polyposis (FAP). a reduced amount of mutant transcript or impaired transcript function.5 Although extra-intestinal manifestations are limited in AFAP,4 higher incidences of desmoid tumours have been associated with 3 mutations.6 CRC risk is well defined for families of individuals with adenomatous polyps.7 However, the risk for those with AFAP is less well characterised and has, to our knowledge, only been evaluated for a single AFAP-associated mutation.8 In this study, we identified a novel germline mutation present in seven families from the Tayside region of Scotland with a presentation of autosomal dominant late-onset CRC. In addition, we have been able to link three of these families to a pair of common ancestors, suggesting the presence of a founder effect in this population. Furthermore, we characterised the risk of CRC in these mutation carriers. Ultimately, these data enhance understanding of AFAP and informs the development of effective guidelines in its clinical management. Materials and methods Patients This study was conducted with Caldicott Guardian approval for analysis of anonymised data. Families were ascertained through affected probands. Probands were referred to the clinic on the basis of a history of rectal bleeding, right-sided polyps, and/or family history of CRC. Classical FAP phenotype was excluded, and DNA microsatellite instability analyses in seven probands excluded HNPCC or Lynch syndrome. No cases of CRC were detected on surveillance colonoscopy. The seven families in this study comprise 255 individuals. The mean (SD) age was 52.5 years (20.7) whereas the mean (SD) age of CRC onset was 61.7 years (10.5), range 32C80 years. In addition to the 23 mutation carriers, 13 individuals were identified as obligate mutation carriers. Data used for analysis are summarised in Table 1. Furthermore, three families were identified as sharing a pair of common ancestors (Physique 1) and for the purposes of the modified segregation analysis were treated as a single pedigree. Physique 1 Pedigree of three attenuated familial adenomatous polyposis families. Probands are indicated with an arrow. Shading refers to colorectal cancer. Positive symbols indicate mutation carriers, while negative symbols … Table 1 Segregation analysis for mutation Mutation analysis Mutation analysis of the gene (“type”:”entrez-nucleotide”,”attrs”:”text”:”NM_000038.5″,”term_id”:”307133686″,”term_text”:”NM_000038.5″NM_000038.5) was performed using standard clinical protocols. These included PCR amplification and bi-directional sequencing of each exon (according to “type”:”entrez-nucleotide”,”attrs”:”text”:”NM_000038.5″,”term_id”:”307133686″,”term_text”:”NM_000038.5″NM_000038.5) of the gene.9 Variant data were submitted to the Leiden Open Variation Database (http://www.lovd.nl/APC). LAMB2 antibody Statistical methods For all analyses, we considered time to CRC diagnosis for each family member. We assumed a censoring process such that an individual was followed from birth until the age at CRC diagnosis, age of death, age at last observation, or age 85 years C whichever occurred first. All individuals with censoring ages 85 years were censored as unaffected at age 85 years. In the instance of no available age information, we censored at age 0 years. All assessments of statistical significance were two-sided, and we used a statistical significance threshold of mutation. For this purpose, we modelled the retrospective likelihood of observing pedigree genotypes and phenotypes of all family members conditional on pedigree disease phenotypes of all family members and genotype of the first identified mutation carrier in each family. This is in line with the sequential ascertainment adjustment procedure TAK-960 of Cannings and Thomson10 allowing us to obtain unbiased parameter estimates. We assumed that this prevalence of the mutation in the population was rare (prevalence=0.001), but our results were not sensitive to this assumption. All models were parameterised in terms of TAK-960 the log-relative risk TAK-960 parameters and three models were fitted: (i) a standard model estimating a single RR parameter; (ii) a sex-specific model that estimated associations separately for men and women; and (iii) an TAK-960 age-specific model that estimated associations for age strata 0C49 years, 50C59 years, 60C69 years, and 70 years. The RR was assumed to be 1 for individuals aged <20 years. The CRC incidences were constrained over all genetic effects to agree with population incidences,11 and CRC population- and gender-specific incidences were obtained from the Cancer Incidence in Five Continents.