Genetic analysis of 1,826 men linked GALNT3, GALNT8 and GALNTL5 variants to distinct sperm head and tail defects.
Reported ICSI outcomes in variant carriers were broadly comparable with controls, although detailed outcome figures remain limited.
Some men have sufficient sperm numbers but difficulty conceiving because sperm move poorly or have abnormal heads and tails. These abnormalities can have several causes, including hormonal and lifestyle factors. New research suggests that particular gene variants may be important in some cases.
A team including West China Second University Hospital, Sichuan University, analyzed genetic information from 1,148 men with abnormal sperm motility and morphology and 678 fertile men: 1,826 in total. Variants in GALNT3, GALNT8 and GALNTL5 were associated with different structural defects.
Men with identified variants also had broadly similar reported ICSI outcomes to controls, suggesting that assisted reproduction may remain an option despite genetically associated sperm abnormalities.
The study was published online in Fertility and Sterility on October 17, 2026.
Looking for genetic explanations for abnormal sperm structure
Sperm consist of a head, midpiece and tail. The head contains genetic material, while the acrosome at its front is important in fertilization. The tail provides propulsion.
Abnormal development of any of these structures can impair motility or fertilization.
The study focused on asthenoteratozoospermia: reduced sperm movement together with a low proportion of normally shaped sperm.
The team used whole-exome sequencing in men recruited in southwestern China between 2018 and 2024. Immunofluorescence and electron microscopy helped investigate how variants related to sperm structure.
GALNT-family variants were observed more frequently in infertile than fertile men. Some variants predicted to impair function were found in the patient group.
The findings connect motility and morphology abnormalities with genes involved in sperm formation, rather than describing impaired function alone.
Different genes, different defects
The three genes were associated with distinct abnormalities.
GALNT3 variants were linked to globozoospermia, in which sperm have round heads. Failure of the acrosome to develop normally can interfere with fertilization.
GALNT8 variants were associated with severe tail defects, notably loss of the central pair of microtubules important for tail movement. Such a defect can impair motility.
GALNTL5 variants were associated with abnormalities affecting both the head and tail, potentially influencing sperm function more broadly.
The researchers also observed markedly reduced or undetectable expression of the corresponding proteins. GALNT3 was mainly located in the acrosome, GALNT8 in the tail, and GALNTL5 in both head and tail.
These observations support a close relationship between particular variants and structural defects.
Broadly similar reported ICSI outcomes
The ICSI findings are clinically relevant.
ICSI involves selecting a sperm and injecting it directly into the egg’s cytoplasm. It is widely used when motility is very low or few sperm have normal morphology.
The team found no clear overall difference in reported ICSI outcomes between patients carrying GALNT variants and controls.
This suggests that ICSI may remain a treatment option for genetically associated structural abnormalities.
It does not guarantee the same outcome for every carrier. The published abstract did not provide sufficient detailed comparisons of carrier numbers for each gene, fertilization, clinical pregnancy and live birth. The findings should not be interpreted as proving identical birth prospects to those of men without these variants.
When might genetic assessment help?
Routine male fertility assessment examines concentration, movement and shape. Semen analysis does not always explain why sperm structures developed abnormally.
This research suggests that genetic analysis may help identify causes in men with particular morphological defects.
Genetic factors may merit consideration when heads are unusually round or tails have severe structural abnormalities.
This does not mean every man with low motility needs genetic testing. Varicocele, hormonal problems, infection and lifestyle factors can also cause sperm abnormalities.
The study involved men in southwestern China. Findings need validation in other populations, and the effects of individual variants on pregnancy and birth require further study.
Looking beyond sperm numbers
Male fertility assessment needs to consider structural defects, their causes and their effects on fertilization, as well as sperm count.
This study provides clues to the genetic basis of abnormal morphology and motility.
It is also notable that treatment using ICSI remained a possibility among patients with identified variants.
Genetic testing alone cannot predict pregnancy or determine treatment. With severe morphological abnormalities or repeated fertilization failure, a male fertility specialist can assess whether genetic evaluation is appropriate and discuss assisted-reproduction options.
Understanding poor movement and abnormal shape may require examining the genetic processes of sperm formation alongside semen results. These findings may contribute to more precise diagnosis and individualized treatment planning.
This article is based on “Pathogenic variants in GALNT3, GALNT8, and GALNTL5 are associated with distinct sperm defects in human asthenoteratozoospermia,” by researchers including West China Second University Hospital, Sichuan University, published online in Fertility and Sterility on October 17, 2026. DOI: 10.1016/j.fertnstert.2026.10.009. PMID: 42892435.
This article explains research and does not replace individual diagnosis or treatment. Genetic testing and treatment should be discussed with a specialist.
The accompanying image was created using generative AI (ChatGPT, OpenAI); any people depicted are fictional.
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