Identification of a new recurrent aurora kinase C mutation in both European and African men with macrozoospermia.
OBJECTIVE
Can we identify new sequence variants in the aurora kinase C gene (AURKC) of patients with macrozoospermia and establish a genotype-phenotype correlation?


CONCLUSIONS
We identified a new non-sense mutation, p.Y248*, that represents 13% of all mutant alleles. There was no difference in the phenotype of individuals carrying this new mutation versus the initially described and main mutation c.144delC.


BACKGROUND
The absence of a functional AURKC gene causes primary infertility in men by blocking the first meiotic division and leading to the production of tetraploid large-headed spermatozoa. We previously demonstrated that most affected men were of North African origin and carried a homozygous truncating mutation (c.144delC).


METHODS
This is a retrospective study carried out on patients consulting for infertility and described as having >5% large-headed spermatozoa. A total of 87 patients are presented here, 43 patients were published previously and 44 are new patients recruited between January 2008 and December 2011.


METHODS
All patients consulted for primary infertility in fertility clinics in France (n = 44), Tunisia (n = 30), Morocco (n = 9) or Algeria (n = 4). Sperm analysis was carried out in the recruiting fertility clinics and all molecular analyses were performed at Grenoble teaching hospital. DNA was extracted from blood or saliva and the seven AURKC exons were sequenced. RT-PCR was carried out on transcripts extracted from leukocytes from one patient homozygous for p.Y248*. Microsatellite analysis was performed on all p.Y248* patients to evaluate the age of this new mutation.


RESULTS
We identified a new non-sense mutation, p.Y248*, in 10 unrelated individuals of European (n = 4) and North African origin (n = 6). We show that this new variant represents 13% of all mutant alleles and that the initially described c.144delC variant accounts for almost all of the remaining mutated alleles (85.5%). No mutated transcripts could be detected by RT-PCR suggesting a specific degradation of the mutant transcripts by non-sense mediated mRNA decay. A rare variant located in the 3' untranslated region was found to strictly co-segregate with p.Y248*, demonstrating a founding effect. Microsatellite analysis confirmed this linkage and allowed us to estimate a mutational age of between 925 and 1325 years, predating the c.144delC variant predicted by the same method to have arisen 250-650 years ago. Patients with no identified AURKC mutation (n = 15) have significantly improved parameters in terms of vitality and concentration of normal spermatozoa, and a decreased rate of spermatozoa with a large head and multiple flagella (P < 0.001).


CONCLUSIONS
Despite adherence to the World Health Organization guidelines, large variations in most characteristic sperm parameters were observed, even for patients with the same homozygous mutation. We believe that is mainly related to inter-laboratory variability in sperm parameter scoring. This prevented us from establishing clear-cut values to indicate a need for molecular analysis of patients with macrozoospermia.


CONCLUSIONS
This study confirms yet again the importance of AURKC mutations in the aetiology of macrozoospermia. Although a large majority of patients are of North African origin, we have now identified European patients carrying a new non-sense mutation indicating that a diagnosis of absence of a functional AURKC gene should not be ruled out for non-Magrebian individuals. Indirect evidence indicates that AURKC might be playing a role in the meiotic spindle assembly checkpoint (SAC) during meiosis. We postulate that heterozygous men might have a more relaxed SAC leading to a more abundant sperm production and a reproductive advantage. This could be the reason for the rapid accumulation of the two AURKC mutations we observe in North African individuals.


BACKGROUND
None of the authors have any competing interest. This work is part of the project 'Identification and Characterization of Genes Involved in Infertility (ICG2I)' funded by the programme GENOPAT 2009 from the French Research Agency (ANR).
Laboratoire AGIM, CNRS FRE3405, Equipe 'Génétique, Infertilité et Thérapeutiques', La Tronche F-38700,  France.
Mariem
M
Ben Khelifa
Charles
C
Coutton
Michael G B
MG
Blum
Farid
F
Abada
Radu
R
Harbuz
Raoudha
R
Zouari
Agnès
A
Guichet
Pascale
P
May-Panloup
Valérie
V
Mitchell
Jacques
J
Rollet
Chema
C
Triki
Ghaya
G
Merdassi
François
F
Vialard
Isabelle
I
Koscinski
Stéphane
S
Viville
Leila
L
Keskes
Jean Pierre
JP
Soulie
Nathalie
N
Rives
Béatrice
B
Dorphin
Florence
F
Lestrade
Laeticia
L
Hesters
Catherine
C
Poirot
Brigitte
B
Benzacken
Pierre-Simon
PS
Jouk
Véronique
V
Satre
Sylviane
S
Hennebicq
Christophe
C
Arnoult
Joël
J
Lunardi
Pierre F
PF
Ray
D000328:Adult; D000462:Algeria; D064108:Aurora Kinase C; D064127:Aurora Kinases; D018389:Codon, Nonsense; D015331:Cohort Studies; D003434:Crossing Over, Genetic; D005091:Exons; D018703:Founder Effect; D005602:France; D056726:Genetic Association Studies; D006801:Humans; D007248:Infertility, Male / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009018:Morocco; D009154:Mutation; D010375:Pedigree; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D012189:Retrospective Studies; D013077:Sperm Head / Q000473:pathology; D013094:Spermatozoa / Q000002:abnormalities* / Q000473:pathology; D014416:Tunisia
D018389:Codon, Nonsense; C576927:AURKC protein, human; D064108:Aurora Kinase C; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases