Biology subjects

Houston, B. J.

Publications and source records attributed to Houston, B. J..

6 recordsLinked to original sources

bioRxiv2024

Mammalian heat shock protein A4 family ortholog Hsc70Cb is required for two phases of spermatogenesis in D. melanogaster

Heat shock proteins play essential roles as molecular chaperones, enacting protein folding and preventing of protein aggregation. In a previous study, a predicted damaging homozygous non-synonymous genetic variant was detected in the heat shock protein gene HSPA4L. Here, we used RNA interference in Drosophila melanogaster to explore the role of the heat shock protein A member 4 family (HSPA4) family in male fertility. Expression of the fly orthologue of the mammalian HSPA4 and HSPA4L genes, Hsc70Cb, was ablated in the male germline using two RNAi lines and the Nanos-Gal4 driver. Strong knockdown of Hsc70Cb in male germ cells resulted in male sterility, characterised by the absence of germ cells in testes and the over-proliferation of the testis soma. A less robust knockdown of Hsc70Cb in the male germline resulted in a sperm individualisation defect and a failure of sperm release into the seminal vesicle (analogous to the epididymis). When human HSPA4 or HSPA4L cDNA was introduced into infertile Hsc70Cb mutant flies, a partial rescue was observed, whereby in the robust Hsc70Cb knockdown setting germ cells progressed to the spermatocyte stage before undergoing cell death. Collectively, the absence of sperm in the Hsc70Cb (line 1) is consistent with the infertile man harbouring a homozygous HSPA4L genetic variant, supporting the hypothesis that HSPA4L is required for male fertility in humans and flies and highlighting the utility of the fly as a model of human spermatogenesis. In briefHsc70Cb is essential for spermatogonia survival and sperm individualisation in Drosophila. This study highlights the conserved roles of the HSPA4 family across animals and the utility of flies as a model organism for male fertility research.

genetics↗

bioRxiv2024

A novel CCDC112-dependent process of sperm midpiece formation and epididymal maturation

The sperm mitochondrial sheath has proposed functions in structural support and energy production for motility. Here we define coiled coil domain containing protein 112, CCDC112, as crucial for male fertility, specifically in the assembly and function of the mitochondrial sheath. We unveiled a previously unrecognised process of epididymal mitochondrial sheath maturation. Sperm mitochondrial sheaths are structurally immature upon exiting the testis and continue to mature as they transit from the caput to the cauda epididymis. Data reveal the critical role of CCDC112 in mitochondrial morphogenesis during sheath formation. A lack of CCDC112 lead to significantly reduced mitochondrial respiration capacity, irregular flagellar waveforms, diminished progressive motility and a failure of sperm to traverse the female reproductive tract to the site of fertilisation and penetrate the zonae pellucidae of oocytes. Finally, we identify CCDC112 as a component of the distal appendages of the mother centriole and identify a facilitative role in core tail assembly. Collectively, CCDC112 is a key regulator of sperm mitochondrial sheath assembly while further expanding the understanding of spermatogenesis, energy generation and flagella kinematics.

developmental biology↗

bioRxiv2023

AXDND1 is required to balance spermatogonial commitment and for sperm tail formation in mice and humans

Dynein complexes are large, multi-unit assemblies involved in many biological processes including male fertility via their critical roles in protein transport and axoneme motility. Previously we identified a pathogenic variant in the dynein gene AXDND1 in an infertile man. Subsequently we identified an additional four potentially compound heterozygous variants of unknown significance in AXDND1 in two additional infertile men. We thus tested the role of AXDND1 in mammalian male fertility by generating a knockout mouse model. Axdnd1-/- males were sterile at all ages but could undergo one round of histologically complete spermatogenesis. Subsequently, a progressive imbalance of spermatogonial commitment to spermatogenesis over self-renewal occurred, ultimately leading to catastrophic germ cell loss, loss of blood-testis barrier patency and immune cell infiltration. Sperm produced during the first wave of spermatogenesis were immotile due to abnormal axoneme structure, including the presence of ectopic vesicles and abnormalities in outer dense fibres and microtubule doublet structures. Sperm output was additionally compromised by a severe spermiation defect and abnormal sperm individualisation. Collectively, our data highlight the essential roles of AXDND1 as a regulator of spermatogonial commitment to spermatogenesis and during the processes of spermiogenesis where it is essential for sperm tail development, release and motility.

cell biology↗

bioRxiv2023

CEP76 is a critical regulator of male germ cell transition zone function and tail composition

The transition zone is a specialised gate at the base of cilia/flagella, which segregates the ciliary compartment from the cytoplasm and strictly regulates protein entry. In this study, we have identified CEP76 as an essential germ cell transition zone protein, involved in the selective entry and incorporation of key proteins required for sperm function and fertility into the ciliary compartment and ultimately the sperm tail. In its absence sperm tails are shorter and immotile as a consequence of deficits in essential sperm motility proteins including DNAH2 and AKAP4, which accumulate at the sperm neck in the mutant. We demonstrate CEP76 is required for sperm tail fibrous sheath formation, outer dense fibre loading and axoneme stability in the principal piece and ultimately sperm motility. Finally, we identify that CEP76 dictates annulus positioning and composition, adding further evidence that the spermatid transition zone and annulus are part of the same functional structure.

cell biology↗

bioRxiv2022

Male mammalian meiosis and spermiogenesis is critically dependent on the shared functions of the katanins KATNA1 and KATNAL1

Katanin microtubule severing enzymes are potent M-phase regulators in oocytes and somatic cells. How the complex, and evolutionarily critical, male mammalian meiotic spindle is sculpted remains unknown. Here, using multiple single and double gene knockout mice, we reveal that the canonical katanin A-subunit, KATNA1, and its close paralogue, KATNAL1, together execute multiple aspects of meiosis. We show KATNA1 and KATNAL1 collectively regulate the male meiotic spindle, cytokinesis and midbody abscission, in addition to diverse spermatid remodelling events, including Golgi organisation, and acrosome and manchette formation. We also define KATNAL1-specific roles in sperm flagella development, manchette regulation, and sperm-epithelial disengagement. Finally, using proteomic approaches we define the KATNA1, KATNAL1, and KATNB1 mammalian testis interactome, which includes a network of cytoskeletal and vesicle trafficking proteins. Collectively, we reveal the presence of multiple katanin A-subunit paralogs in mammalian spermatogenesis allows for customized cutting via neofunctionalization and protective buffering via gene redundancy.

cell biology↗

bioRxiv2021

A de novo paradigm for male infertility

IntroductionDe novo mutations (DNMs) are known to play a prominent role in sporadic disorders with reduced fitness1. We hypothesize that DNMs play an important role in male infertility and explain a significant fraction of the genetic causes of this understudied disorder. To test this hypothesis, we performed trio-based exome-sequencing in a unique cohort of 185 infertile males and their unaffected parents. Following a systematic analysis, 29 of 145 rare protein altering DNMs were classified as possibly causative of the male infertility phenotype. We observed a significant enrichment of Loss-of-Function (LoF) DNMs in LoF-intolerant genes (p-value=1.00x10-5) as well as predicted pathogenic missense DNMs in missense-intolerant genes (p-value=5.01x10-4). One DNM gene identified, RBM5, is an essential regulator of male germ cell pre-mRNA splicing2. In a follow-up study, 5 rare pathogenic missense mutations affecting this gene were observed in a cohort of 2,279 infertile patients, with no such mutations found in a cohort of 5,784 fertile men (p-value=0.009). Our results provide the first evidence for the role of DNMs in severe male infertility and point to many new candidate genes affecting fertility.

genetics↗