Medical Genetics

Genetics & Biology: The APC Gene and Inheritance

At a Glance

Gardner syndrome is caused by a mutation in the APC gene, which normally stops cells from growing out of control. It has a 50% chance of being passed to children. Knowing the exact location of your mutation, or codon, helps doctors predict symptom risks and tailor your medical care.

The biological root of Gardner syndrome lies in a single gene called APC (Adenomatous Polyposis Coli). Understanding how this gene works—and what happens when it doesn’t—is the first step in moving from uncertainty to empowered management of your health.

The APC Gene: Your Body’s Natural Brake Pedal

The APC gene is what scientists call a tumor suppressor gene ^[1]^[2]. Its job is to create a protein that acts like a “brake pedal” for cell growth.

Under normal conditions, this protein manages a messenger in your cells called beta-catenin ^[3]. Beta-catenin’s job is to tell cells to divide and grow. The APC protein keeps beta-catenin levels low so that cells only grow when they are supposed to ^[3]^[4].

In Gardner syndrome, the APC gene has a mutation (a “typo” in the genetic code) that prevents it from making a functional brake protein ^[5]^[6]. Without this brake, beta-catenin builds up and continuously signals your cells to divide. This unchecked growth is what leads to the formation of hundreds of polyps in the colon and the various growths outside the colon ^[6]^[7].

Inheritance: The 50/50 Rule

Gardner syndrome/FAP follows a pattern called autosomal dominant inheritance ^[1]^[8]. Here is what that means for you and your family:

Autosomal: The gene is located on one of the numbered chromosomes, not the sex chromosomes (X or Y). It affects men and women equally.
Dominant: You only need one copy of the mutated gene (from one parent) to have the condition.
The Odds: If a parent has the mutation, there is a 50% chance with each pregnancy that the mutation will be passed to their child ^[1]^[2].

It is important to note that about 25% of people diagnosed with an APC mutation are the first in their family to have it; this is called a de novo or “new” mutation.

Family Planning

For those planning a family, knowing your exact mutation opens the door to Preimplantation Genetic Testing (PGT-M) during IVF. This allows doctors to test embryos and ensure the APC mutation is not passed to the next generation ^[8].

The Concept of Genotype-Phenotype Correlation

One of the most powerful pieces of information you can own is your exact genotype—the specific location of the “typo” on your APC gene. Doctors refer to these locations as codons (which are like page numbers in a book). Where your mutation is located often correlates with your phenotype (how the disease actually looks and behaves in your body) ^[9]^[10]:

Mutation Location and Polyp Density: Mutations at certain codons (like codon 1309) are often associated with “classic” FAP, involving thousands of polyps. Mutations at the very beginning or end of the gene are often associated with “attenuated” (milder) FAP, with fewer polyps ^[11]^[12].
Desmoid Tumor Risk: Mutations further down the gene (specifically toward the “3’ end” or after codon 1400) are sometimes linked to a higher risk of developing desmoid tumors ^[13]^[14].
Eye Markers (CHRPE): Mutations between codons 311 and 1444 are often associated with small, harmless dark spots on the retina of the eye, called CHRPE ^[15]^[16].

Why Your Results Matter

While these correlations help doctors predict risks, they are not a crystal ball. Even people in the same family with the exact same mutation can have different experiences ^[17]^[18]. However, knowing your specific mutation helps your care team tailor your surveillance ^[19]^[20].

Your Action Step: Ask your doctor for a copy of your molecular genetic test report. Look for the specific “codon” or “pathogenic variant” listed. This document is a critical piece of your medical history that you should keep forever.

Common questions in this guide

How is Gardner syndrome inherited?

Gardner syndrome follows an autosomal dominant inheritance pattern. This means that if one parent has the mutated APC gene, there is a 50% chance with each pregnancy that the mutation will be passed to the child.

What does the APC gene do, and what happens when it is mutated?

The APC gene normally acts like a brake pedal for cell growth. When it is mutated, cells divide uncontrollably, leading to the formation of hundreds of colon polyps and other tumors throughout the body.

What is a de novo mutation in Gardner syndrome?

A de novo mutation means the genetic change happened spontaneously rather than being passed down. About 25% of people diagnosed with an APC mutation are the first in their family to have it.

Why does the specific location (codon) of my APC mutation matter?

The exact location of the genetic typo is called a codon. Knowing your specific codon helps doctors predict how the disease will behave, including your risk for desmoid tumors, thousands of polyps, or an attenuated form of the disease.

Can I prevent passing Gardner syndrome to my children?

Yes, if you know your exact mutation, you can use Preimplantation Genetic Testing (PGT-M) during in vitro fertilization (IVF). This allows doctors to test embryos and ensure the condition is not passed to the next generation.

Curated prompts to bring to your next appointment.

1.What is the exact 'codon' or location of my mutation on the APC gene?
2.Does the location of my mutation suggest a higher risk for desmoid tumors or dental issues?
3.Is my mutation considered a 'de novo' mutation, or is it likely inherited?
4.Does the location of my mutation correlate with 'attenuated' or 'classic' FAP?
5.Should my children or siblings be tested for this specific mutation, and at what age?

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References (20)

1
Targeted next-generation sequencing approach for molecular genetic diagnosis of hereditary colorectal cancer: Identification of a novel single nucleotide germline insertion in adenomatous polyposis coli gene causes familial adenomatous polyposis.
Wang D, Liang S, Zhang X, et al.
Molecular genetics & genomic medicine 2019; (7(1)):e00505 doi:10.1002/mgg3.505.
PMID: 30523670
2
Familial Adenomatous Polyposis.
Waller A, Findeis S, Lee MJ
Journal of pediatric genetics 2016; (5(2)):78-83 doi:10.1055/s-0036-1579760.
PMID: 27617147
3
The two SAMP repeats and their phosphorylation state in Drosophila Adenomatous polyposis coli-2 play mechanistically distinct roles in negatively regulating Wnt signaling.
Kunttas-Tatli E, Von Kleeck RA, Greaves BD, et al.
Molecular biology of the cell 2015; (26(24)):4503-18 doi:10.1091/mbc.E15-07-0515.
PMID: 26446838
4
miR‑501‑3p promotes colorectal cancer progression via activation of Wnt/β‑catenin signaling.
Wu F, Xing T, Gao X, Liu F
International journal of oncology 2019; (55(3)):671-683 doi:10.3892/ijo.2019.4852.
PMID: 31364752
5
Mutational screening through comprehensive bioinformatics analysis to detect novel germline mutations in the APC gene in patients with familial adenomatous polyposis (FAP).
Ghadamyari F, Heidari MM, Zeinali S, et al.
Journal of clinical laboratory analysis 2021; (35(5)):e23768 doi:10.1002/jcla.23768.
PMID: 33769591
6
Aberrant β-Catenin Expression and Its Association With Epithelial-Mesenchymal Transition and Clinical Outcomes of Colorectal Cancer.
Hussein ZH, Hassawi BA, Ibraheem Q
Cureus 2024; (16(1)):e53104 doi:10.7759/cureus.53104.
PMID: 38414697
7
OTX1 promotes tumorigenesis and progression of cervical cancer by regulating the Wnt signaling pathway.
Zhou L, Li H, Zhang D, et al.
Oncology reports 2022; (48(5)).
PMID: 36177903
8
A novel large germ line deletion in adenomatous polyposis coli (APC) gene associated with familial adenomatous polyposis.
Pouya F, Mojtabanezhad Shariatpanahi A, Ghaffarzadegan K, et al.
Molecular genetics & genomic medicine 2018; (6(6)):1031-1040 doi:10.1002/mgg3.479.
PMID: 30259713
9
Attenuated Familial Adenomatous Polyposis: A Phenotypic Diagnosis but Obsolete Term?
Anele CC, Martin I, McGinty Duggan PM, et al.
Diseases of the colon and rectum 2022; (65(4)):529-535 doi:10.1097/DCR.0000000000002217.
PMID: 34775416
10
The genetic basis of colonic adenomatous polyposis syndromes.
Talseth-Palmer BA
Hereditary cancer in clinical practice 2017; (15()):5 doi:10.1186/s13053-017-0065-x.
PMID: 28331556
11
Abdominal Desmoid: Course, Severe Outcomes, and Unique Genetic Background in a Large Local Series.
Ophir G, Sivan S, Hana S, et al.
Cancers 2021; (13(15)) doi:10.3390/cancers13153673.
PMID: 34359575
12
Attenuated adenomatous polyposis of the large bowel: Present and future.
Roncucci L, Pedroni M, Mariani F
World journal of gastroenterology 2017; (23(23)):4135-4139 doi:10.3748/wjg.v23.i23.4135.
PMID: 28694653
13
A Patient With Desmoid Tumors and Familial FAP Having Frame Shift Mutation of the APC Gene.
Sadighi S, Ghaffari-Moghaddam M, Saffari M, et al.
Acta medica Iranica 2017; (55(2)):134-138.
PMID: 28282712
14
Aggressive mutation in a familial adenomatous polyposis syndrome family: when phenotype guides clinical surveillance.
Neffa F, Garcia L, Della Valle A, et al.
Journal of gastrointestinal oncology 2018; (9(3)):553-559 doi:10.21037/jgo.2017.10.06.
PMID: 29998021
15
Use of congenital hypertrophy of the retinal pigment epithelium as a clinical sign of familial adenomatous polyposis.
Carvalho AA, Crespo TS, Násser LS, et al.
Arquivos brasileiros de oftalmologia 2024; (88(3)) doi:10.5935/0004-2749.2023-0115.
PMID: 39607153
16
Study of diagnostic value of congenital hypertrophy of retinal pigment epithelium in Chinese familial adenomatous polyposis patients.
Cai S, Yu Y, Xie X, et al.
European journal of cancer prevention : the official journal of the European Cancer Prevention Organisation (ECP) 2022; (31(5)):422-429 doi:10.1097/CEJ.0000000000000725.
PMID: 35191403
17
The role of mutation analysis of the APC gene in the management of FAP patients. A controversial issue.
Dodaro C, Grifasi C, Florio J, et al.
Annali italiani di chirurgia 2016; (87()):321-325.
PMID: 27682830
18
APC and MUTYH Analysis in FAP Patients: A Novel Mutation in APC Gene and Genotype-Phenotype Correlation.
D'Elia G, Caliendo G, Casamassimi A, et al.
Genes 2018; (9(7)) doi:10.3390/genes9070322.
PMID: 29954149
19
Two cases of genetic testing for familial adenomatous polyposis without a family history.
Makutani Y, Iwamoto M, Daito K, et al.
International cancer conference journal 2025; (14(4)):387-395 doi:10.1007/s13691-025-00782-x.
PMID: 41395568
20
Updated European guidelines for clinical management of familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), gastric adenocarcinoma, proximal polyposis of the stomach (GAPPS) and other rare adenomatous polyposis syndromes: a joint EHTG-ESCP revision.
Zaffaroni G, Mannucci A, Koskenvuo L, et al.
The British journal of surgery 2024; (111(5)) doi:10.1093/bjs/znae070.
PMID: 38722804

This page explains the genetics of Gardner syndrome and the APC gene for educational purposes only. Always consult a genetic counselor or your medical team to interpret your specific genetic test results.

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