FBXL13 rs372229746: What Your Genotype Means
The genetic variant rs372229746 is a low-frequency polymorphism located within the FBXL13 gene locus. Research has identified this variant as being associated with human chronotype, which refers to an individual's natural preference for morningness or eveningness.
What each genotype means
Typical diurnal preference
This genotype represents the most common state at this locus in the general population. Research indicates that individuals with this genotype do not carry the specific variant associated with shifts in chronotype or diurnal preference at the FBXL13 locus.
This is the most common genotype, found in the vast majority of individuals across global populations.
Potential chronotype shift
Carrying one copy of this variant has been statistically associated with variations in self-reported chronotype, or diurnal preference, in large-scale population studies. Because chronotype is a complex trait influenced by many genetic and environmental factors, this genotype is only one small contributor to your overall sleep-wake timing.
This genotype is carried by approximately 3% of individuals in populations where this variant has been studied.
Potential chronotype shift
Carrying two copies of this variant has been associated with shifts in diurnal preference in large-scale genome-wide association studies. While this variant is linked to circadian rhythm traits, it does not determine your sleep schedule, as many other genetic and lifestyle factors play a significant role in your personal chronotype.
This genotype is rare, occurring in less than 1% of the population based on current biobank data.
Understanding the Variant
The variant rs372229746 is a single nucleotide polymorphism (SNP) situated in the genomic region of the FBXL13 gene. In genetics, a SNP represents a variation at a single position in a DNA sequence among individuals. While many SNPs are common, rs372229746 is considered a low-frequency variant, meaning it is found in only a small percentage of the general population. This specific location has been highlighted in large-scale genome-wide association studies (GWAS) as a site of interest for researchers studying the biological underpinnings of sleep and circadian rhythms. Because it is a regulatory variant, it is thought to influence how the nearby gene is expressed rather than necessarily changing the structure of the protein it produces.
The Role of FBXL13
The FBXL13 gene encodes a protein that is part of the F-box protein family. These proteins are essential components of the SCF (SKP1-CUL1-F-box protein) ubiquitin ligase complex, which plays a critical role in the degradation of various proteins within the cell. In the context of circadian biology, the regulation of protein stability is vital for maintaining the 24-hour internal clock. While the exact mechanism by which FBXL13 influences sleep timing is still being investigated, its identification in studies of chronotype suggests that it may help regulate the turnover of proteins involved in the circadian clock machinery. By modulating the stability of these clock-related proteins, FBXL13 may contribute to the subtle differences in sleep-wake cycles observed across the human population.
Research and Evidence
The association between rs372229746 and chronotype was identified through large-scale population biobanks, such as the UK Biobank. Researchers compared the genetic data of thousands of individuals with their self-reported sleep preferences to find statistical links between specific variants and sleep timing. The evidence for this association is considered moderate, as it emerged from genome-wide scans that identify signals across the entire human genome. It is important to note that while these associations are statistically significant, they represent small contributions to a complex trait. Chronotype is a polygenic trait, meaning it is influenced by hundreds of different genetic variants, as well as environmental factors like light exposure, work schedules, and lifestyle choices. Therefore, this single variant does not determine an individual's sleep schedule.
Interpreting Your Results
If you encounter this variant in a genetic report, it is essential to understand that it is not a diagnostic tool. The presence of a specific genotype at rs372229746 does not mean you have a sleep disorder or a fixed, unchangeable sleep schedule. Because the effect size of this variant is small, it is not used in clinical settings to predict individual health outcomes or to guide medical treatment. Genetic associations are population-level observations, not individual predictions. If you are experiencing significant sleep issues, such as chronic insomnia or excessive daytime sleepiness, these are complex medical concerns that require professional evaluation. You should consult with a healthcare provider or a sleep specialist who can assess your symptoms, medical history, and lifestyle to provide appropriate guidance or treatment.
How common is this variant?
The variant rs372229746 is a low-frequency polymorphism with a minor allele frequency (MAF) typically reported between 0.01 and 0.03 across diverse populations.
Frequently asked questions
Does this variant mean I am a 'night owl' or a 'morning lark'?
No, this variant is only one of many genetic factors that contribute to your chronotype. It does not determine your sleep preference, and environmental factors play a much larger role in your daily sleep habits.
Can I use this information to change my sleep schedule?
No, this information is for educational purposes only and cannot be used to guide lifestyle changes or medical decisions. If you are struggling with your sleep schedule, consult a doctor for personalized advice.
Is rs372229746 associated with any diseases?
Current research focuses on its association with chronotype and circadian rhythm preferences in the general population. It is not currently classified as a diagnostic marker for any specific sleep disorder.
Why is the evidence for this variant considered moderate?
Evidence is considered moderate because the association was identified through statistical analysis of large population cohorts. While the signal is statistically significant, the biological mechanism is still being studied and the effect size is relatively small.
Sources & further reading
Educational information only, last refreshed 9/20/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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