Cone-Rod Dystrophy With Decreased Male Fertility

Clinical Characteristics
Ocular Features: 

Features of a cone dystrophy appear first followed by rod damage although the course of degeneration is variable.  Poor vision may be present in some individuals in the first years of life but has a later onset in others.  Evidence for rod dysfunction appears later in most patients.

A hyperfluorescent area centered on the fovea can often be seen although there may be patchy areas elsewhere in the fundus.  Foveal atrophy is present in individuals generally after the 5th decade of life. Full field ERG shows reduced or absent cone responses with variable rod responses with more pronounced changes in older individuals.  Variable pigmentation can be seen in the peripapillary area.

Systemic Features: 

The only systemic abnormality thus far identified is a reduction in sperm count and reduced motility.  The resulting loss of fertility, however, occurs only in male patients with truncating variants in TTLL5 and not in those with missense mutations according to the most recent studies.

Genetics

This autosomal recessive condition results from homozygous or compound heterozygous mutations in the TTLL5 gene (14q24.3).  TTLL5 is localized at the base of the spermatozoal axoneme and at the basal body of the cilia in photoreceptors.  

Interestingly, male mice with mutations in this gene have reductions in sperm motility with evident disruption in the formation of sperm tails.

Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

Mutations in the polyglutamylase gene TTLL5, expressed in photoreceptor cells and spermatozoa, are associated with cone-rod degeneration and reduced male fertility

Bedoni N, Haer-Wigman L, Vaclavik V, Tran HV, Farinelli P, Balzano S, Royer-Bertrand B, El-Asrag ME, Bonny O, Ikonomidis C, Litzistorf Y, Nikopoulos K, Yioti G, Stefaniotou M, McKibbin M, Ellingford J, Booth AP, Black G, Toomes C, Inglehearn CF, Hoyng CB, Bax N, Klaver CC, Thiadens AA, Murisier F, Schorderet DF, Ali M, Cremers FP, Andreasson S, Munier FL, Rivolta C. Mutations in the polyglutamylase gene TTLL5, expressed in photoreceptor cells and spermatozoa, are associated with cone-rod degeneration and reduced male fertility. Hum Mol Genet. 2016 Aug 22. pii: ddw282. [Epub ahead of print].

PubMed ID: 
27554115

Biallelic variants in TTLL5, encoding a tubulin glutamylase, cause retinal dystrophy

Sergouniotis PI, Chakarova C, Murphy C, Becker M, Lenassi E, Arno G, Lek M, MacArthur DG; UCL-Exomes Consortium, Bhattacharya SS, Moore AT, Holder GE, Robson AG, Wolfrum U, Webster AR, Plagnol V. Biallelic variants in TTLL5, encoding a tubulin glutamylase, cause retinal dystrophy. Am J Hum Genet. 2014 May 1;94(5):760-9.

PubMed ID: 
244791901

References

Bedoni N, Haer-Wigman L, Vaclavik V, Tran HV, Farinelli P, Balzano S, Royer-Bertrand B, El-Asrag ME, Bonny O, Ikonomidis C, Litzistorf Y, Nikopoulos K, Yioti G, Stefaniotou M, McKibbin M, Ellingford J, Booth AP, Black G, Toomes C, Inglehearn CF, Hoyng CB, Bax N, Klaver CC, Thiadens AA, Murisier F, Schorderet DF, Ali M, Cremers FP, Andreasson S, Munier FL, Rivolta C. Mutations in the polyglutamylase gene TTLL5, expressed in photoreceptor cells and spermatozoa, are associated with cone-rod degeneration and reduced male fertility. Hum Mol Genet. 2016 Aug 22. pii: ddw282. [Epub ahead of print].

PubMedID: 27554115

Sergouniotis PI, Chakarova C, Murphy C, Becker M, Lenassi E, Arno G, Lek M, MacArthur DG; UCL-Exomes Consortium, Bhattacharya SS, Moore AT, Holder GE, Robson AG, Wolfrum U, Webster AR, Plagnol V. Biallelic variants in TTLL5, encoding a tubulin glutamylase, cause retinal dystrophy. Am J Hum Genet. 2014 May 1;94(5):760-9.

PubMedID: 244791901