PER3 rs139315125: Circadian Rhythms and Sleep Phase
The rs139315125 variant is a rare single nucleotide polymorphism located in the PER3 gene, which encodes a key component of the human molecular circadian clock. Research has associated this variant, frequently observed in tandem with the rs150812083 missense mutation, with familial advanced sleep phase syndrome and extreme morning diurnal preference. Carrying the variant shifts the timing of the body's internal daily rhythms, causing earlier natural sleep onset and morning awakening.
What each genotype means
Common circadian genotype
This is the most common genotype observed in the general population. Research into this specific variant, rs139315125, is limited, but it has been identified in studies investigating familial advanced sleep phase syndrome. As this is a rare variant, its specific impact on your individual sleep-wake timing remains uncertain.
This is the most frequent genotype found in the general population.
Rare variant carrier
You carry one copy of the minor allele for this variant. This specific genetic change has been reported in families affected by advanced sleep phase syndrome, a condition characterized by sleep-wake timing that is earlier than typical. Because this variant is rare, its clinical significance for any individual is not fully established.
This genotype is rare, occurring in less than 0.02% of the population according to gnomAD data.
Rare variant homozygote
You carry two copies of the minor allele for this variant. This variant has been associated with familial advanced sleep phase syndrome in research settings, which may influence your internal body clock and sleep timing. Please consult with a sleep specialist or healthcare provider if you have concerns regarding your sleep patterns or circadian rhythm.
This genotype is extremely rare in the general population.
Genomic Location and the PER3 His417Arg Variant
The single nucleotide polymorphism rs139315125 represents a coding missense change (c.1250A>G) located within exon sequences of the PER3 (period circadian regulator 3) gene on human chromosome 1. At the protein level, this base substitution alters codon 417, exchanging an evolutionary conserved histidine for an arginine residue (p.His417Arg). In published medical literature and public genomic repositories, rs139315125 has been documented in high linkage disequilibrium on the exact same haplotype alongside a neighboring variant, rs150812083 (p.Pro415Ala). Together, these twin amino acid changes alter the structural properties of the PER3 protein, influencing how the core circadian machinery assembles and processes diurnal time signals in human cells.
The Biological Role of PER3 in Circadian Timekeeping
The PER3 protein forms an integral cog in the transcription-translation feedback loop that drives mammalian circadian rhythms. In typical physiology, heterodimers of the CLOCK and BMAL1 (ARNTL) transcription factors promote the rhythmic expression of the PERIOD (PER1, PER2, PER3) and CRYPTOCHROME (CRY1, CRY2) genes. As PER and CRY proteins accumulate in the cytoplasm, they form complexes that translocate back into the cell nucleus to repress CLOCK:BMAL1 activity, thereby switching off their own transcription until protein degradation resets the cycle roughly every 24 hours. Functional studies indicate that the p.His417Arg variant in PER3 impairs protein stability and repressor activity, directly modifying the velocity and phase coordination of the internal cellular clock.
Evidence for Familial Advanced Sleep Phase Syndrome
Clinical interest in rs139315125 centers primarily on its association with familial advanced sleep phase syndrome (FASPS3), an autosomal dominant condition characterized by a persistent and involuntary phase advancement of sleep-wake schedules. Individuals carrying this alteration exhibit sleep onset hours earlier than conventional norms—often between 6:00 PM and 9:00 PM—coupled with regular spontaneous waking between 2:00 AM and 5:00 AM. Family pedigree analyses and laboratory models have demonstrated that this variant co-segregates with extreme morningness and altered diurnal phase parameters, occasionally with seasonal mood vulnerabilities. However, because evidence is derived from specialized familial cohorts and candidate sequencing studies, its penetrance and phenotypic impact across broader population backgrounds remain an area of ongoing investigation.
Population Frequency and Allelic Rarity
According to large-scale sequencing datasets such as the Genome Aggregation Database (gnomAD), rs139315125 is an exceptionally rare variant in the general human population, registering an overall minor allele frequency well below 0.0002. The vast majority of people worldwide inherit the ancestral homozygous AA genotype and do not carry the G allele. Because the variant has been identified in a limited number of families of European descent presenting with pronounced shifts in sleep timing, baseline population frequency figures remain low across all cataloged continental ancestries, with homozygotes for the alternative allele virtually unobserved in broad genomic registries.
Contextualizing Genetic Findings and Sleep Health
Detecting an rs139315125 genotype provides biological insight into personal circadian architecture, but it does not serve as an independent diagnostic test or medical verdict. Circadian timing and chronotype are complex, multifactorial traits influenced by dozens of common genetic markers, daily light exposure, work schedules, and sleep hygiene practices. While carrying the rare variant may help explain a lifelong drive toward extreme morningness, it does not constitute a disease on its own. Individuals experiencing persistent social jet lag, daytime sleepiness, or difficulty aligning work demands with their sleep schedule should seek comprehensive evaluation from a board-certified sleep specialist rather than attempting self-directed clinical interventions.
How common is this variant?
The rs139315125 variant is exceptionally rare across global populations, with an estimated minor allele frequency of less than 0.0002 in gnomAD. Almost all cataloged individuals possess the reference AA genotype, with the alternative G allele reported only in rare familial clusters and small patient cohorts.
Frequently asked questions
Does having the rs139315125 variant mean I definitely have a sleep disorder?
No. While the variant has been tracked in families with familial advanced sleep phase syndrome, clinical diagnosis depends on persistent symptoms such as severe difficulty staying awake in the evening and uncontrollable early morning awakening. Lifestyle, light cues, and other genetic variants strongly influence whether an individual experiences a clinical sleep disruption.
What is the difference between an early bird and familial advanced sleep phase?
An early bird or morning lark prefers earlier hours but can generally adapt to social activities or shifted schedules without severe daytime impairment. In familial advanced sleep phase syndrome, the biological clock is hardwired hours ahead of conventional time, making it physiologically impossible to remain awake late into the night regardless of behavioral effort.
Can this genetic variant be modified or treated?
You cannot alter your inherited genetic code, but circadian sleep-wake timing can often be managed through clinical approaches. Circadian rhythm specialists frequently use targeted bright light therapy in the evening and structured behavioral sleep routines to help advance or delay the body's internal clock.
Is rs139315125 related to other common PER3 sleep variants?
Yes, rs139315125 is located in the same PER3 gene as a well-known 4-repeat versus 5-repeat length polymorphism that influences sleep homeostatic pressure and chronotype. However, rs139315125 is a distinct, much rarer single nucleotide change that specifically alters the amino acid sequence at codon 417.
Sources & further reading
Educational information only, last refreshed 9/7/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This SNP is associated with chronotype scores in older adults, suggesting a role in circadian regulation.
This SNP is associated with average delta power during sleep, a marker of sleep intensity.
Missense variant P415A in PER3 associated with familial advanced sleep phase syndrome and circadian phase preference.
Common synonymous variant in PER3 tightly linked with circadian diurnal preference and morningness-eveningness tendencies.
Promoter/intronic variant of PER3 tagging circadian phase angle, diurnal preference, and homeostatic sleep pressure response to sleep loss.
Part of a well-characterized functional haplotype in PER3 influencing individual diurnal preference and susceptibility to delayed sleep phase syndrome.