The POLD1 gene is associated with an increased risk for autosomal dominant colonic adenomatous polyps and colon cancer (PMID: 24509466), and autosomal dominant mandibular hypoplasia, deafness, progeroid features, and lipodystrophy (MDPL) syndrome (MedGen UID: 811623).
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The POLD1 gene encodes the catalytic subunit of DNA polymerase delta, an enzyme that plays a critical role in DNA replication and repair.
MedGen UID: 436445
Pathogenic variants in the POLD1 and POLE genes are associated with a recently defined, highly penetrant autosomal dominant colorectal cancer predisposition syndrome whose proposed name is polymerase proofreading-associated polyposis syndrome (PPAP) (PMID: 24509466, 26133394, 25529843, 26822575). Individuals with a single pathogenic POLD1 variant typically have a more attenuated colorectal phenotype, regularly presenting before the age of 60 with colorectal cancer (often microsatellite stable) or fewer than 100 adenomas (PMID: 25529843, 23263490). The clinical spectrum ranges from large polyps (>2 cm in diameter) to multiple adenomas resembling attenuated familial adenomatous polyposis (AFAP) to MUTYH-associated polyposis syndrome (MAP) (PMID: 25529843). Many cases may also have a family history of clustering of early onset colorectal cancer similar to what is typically seen in Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC), although some have no such history (PMID: 25529843).
PPAP is associated with an increased risk of gastroduodenal (mostly duodenal) adenomas; however, malignancy appears to be limited to those with a POLE pathogenic variant (PMID: 26133394, 25529843, 24788313, 26822575). An individual with a POLD1 pathogenic variant will not necessarily develop cancer in their lifetime, but the risk for cancer is increased over the general population risk.
There is preliminary evidence suggesting those with a single pathogenic variant in this gene may have a predisposition to develop endometrial cancer (PMID: 26133394, 25529843, 23263490, 26822575). These data, however, are currently insufficient to make a clear determination regarding this association. Therefore POLD1 is considered a “preliminary-evidence” gene and is available on Invitae’s Breast and Gyn Cancers Panel. Preliminary-evidence genes are selected from an extensive review of the literature and expert recommendations, but the association between the gene and the specific condition has not been completely established. This uncertainty may be resolved as new information becomes available, and therefore clinicians may continue to order these preliminary evidence genes. The risk for other cancers may also be elevated; however, this evidence is limited and emerging (PMID: 26133394, 25529843, 23263490, 26822575).
The POLD1 gene plays a critical role in DNA replication and repair (Gene. Gene ID: 5424. http://www.ncbi.nlm.nih.gov/gene/5424 Accessed July 2016). POLD1 and POLE encode the catalytic and proofreading subunits of the polymerase enzyme complexes e (Pol d) and d (Pol e), respectively. These subunits are involved in synthesis regulation and cofactor binding (PMID: 25529843). If there is a pathogenic variant in this gene that prevents it from functioning normally, the risk of developing certain types of cancers is increased.
Hereditary predisposition to cancer due to pathogenic variants in the POLD1 gene has autosomal dominant inheritance. This means that an individual with a pathogenic variant has a 50% chance of passing the condition on to their offspring. Once a pathogenic mutation is detected in an individual, it is possible to identify at-risk relatives who can pursue testing for this specific familial variant. Most cases are inherited from a parent, but some cases can occur spontaneously (i.e., an individual with a pathogenic variant has parents who do not have it) (PMID: 25529843). An individual with a variant in POLD1 has a 50% risk of passing that variant on to offspring.
POLD1 is also associated with autosomal dominant mandibular hypoplasia, deafness, progeroid features and lipodystrophy (MDPL) syndrome (MedGen UID: 811623). MPDL is a rare, systemic disorder that is characterized by loss of subcutaneous fat, distinctive facial features, and metabolic abnormalities including insulin resistance and diabetes. Sensorineural hearing loss typically occurs late in the first or second decades of life (PMID: 25131834, 23770608).
Medical management and surveillance protocols for individuals with a pathogenic variant in POLD1 have been developed by the National Comprehensive Cancer Network® (NCCN) (NCCN Clinical Practice Guidelines in Oncology®: Genetic/Familial High-Risk Assessment: Colorectal. Version 1.2016 http://www.nccn.org/professionals/physician_gls/f_guidelines.asp):
An individual’s cancer risk and medical management are not determined by genetic test results alone. Overall cancer risk assessment incorporates additional factors, including personal medical history, family history, and any available genetic information that may result in a personalized plan for cancer prevention and surveillance.
Knowing if a pathogenic variant is present in POLD1 is advantageous. At-risk relatives can be identified, enabling pursuit of a diagnostic evaluation. Further, the available information regarding hereditary cancer susceptibility genes is constantly evolving and more clinically relevant data regarding POLD1 are likely to become available in the near future. Awareness of this cancer predisposition encourages patients and their providers to inform at-risk family members, to diligently follow published screening protocols, and to be vigilant in maintaining close and regular contact with their local genetics clinic in anticipation of new information.
Review Date: July 2016
Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).
Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence, and select noncoding variants. Our assay provides a Q30 quality-adjusted mean coverage depth of 350x (50x minimum, or supplemented with additional analysis). Variants classified as pathogenic or likely pathogenic are confirmed with orthogonal methods, except individual variants that have high quality scores and previously validated in at least ten unrelated samples.
Our analysis detects most intragenic deletions and duplications at single exon resolution. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. If you are requesting the detection of a specific single-exon copy number variation, please contact Client Services before placing your order.
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