Identification of the human ortholog of the t-complex-encoded protein TCTE3 and evaluation as a candidate gene for primary ciliary dyskinesia

Comparative proteomics and phosphoproteomics analysis reveals differential sperm motility in Mediterranean buffalo semen

High motility spermatozoa are good for cryopreservation and artificial insemination (AI) of mammalian semen. In this study, normal motility (NM) and low motility (LM) Mediterranean buffalo spermatozoa were compared using quantitative proteomics and phosphoproteomics techniques to screen for important proteins and phosphorylated proteins related to the motility of spermatozoa and to identify candidate protein molecular markers related to the quality of Mediterranean buffalo semen. Proteomics results identified 2550 proteins, with 119 proteins upregulated and 146 proteins downregulated in the LM spermatozoa versus the NM spermatozoa. The differentially abundant proteins were mainly involved in carbohydrate metabolism, glycolysis/gluconeogenesis, and tricarboxylic acid cycles. The phosphoproteomics analysis revealed 412 proteins, 1228 phosphorylated peptides, and 1465 phosphorylation modification sites. Compared to the NM group, 119 peptides were downregulated in the LM group, corresponding to 98 proteins, and 84 phosphorylated peptides were upregulated in the white matter, corresponding to 61 proteins. Differentially phosphorylated proteins were primarily involved in spermatogenesis, flagellate sperm motility, and glycolysis/gluconeogenesis. The combined proteomics and phosphoproteomics results identified the common proteins HMGB4, POC1B, PKM, LDHA, TBC1D21, and CBY2, whose main roles were related to spermatogenesis, sperm flagellar structure, and energy metabolism, which can be used as potential markers of Mediterranean buffalo sperm quality.

Circadian disruption dysregulates lung gene expression associated with inflammatory lung injury

Rationale

Circadian systems drive the expression of multiple genes in nearly all cells and coordinate cellular-, tissue-, and system-level processes that are critical to innate immunity regulation.

Objective

We examined the effects of circadian rhythm disorganization, produced by light shift exposure, on innate immunity-mediated inflammatory lung responses including vascular permeability and gene expression in a C57BL/6J murine model of inflammatory lung injury.

Methods

A total of 32 C57BL/6J mice were assigned to circadian phase shifting (CPS) with intratracheal phosphate-buffered saline (PBS), CPS with intratracheal lipopolysaccharide (LPS), control (normal lighting) condition with intratracheal PBS, and control condition with intratracheal LPS. Bronchoalveolar lavage (BAL) protein, cell counts, tissue immunostaining, and differentially expressed genes (DEGs) were measured in lung tissues at 2 and 10 weeks.

Measurements and results

In mice exposed to both CPS and intratracheal LPS, both BAL protein and cell counts were increased at both 2 and 10 weeks compared to mice exposed to LPS alone. Multiple DEGs were identified in CPS-LPS-exposed lung tissues compared to LPS alone and were involved in transcriptional pathways associated with circadian rhythm disruption, regulation of lung permeability, inflammation with Rap1 signaling, and regulation of actin cytoskeleton. The most dysregulated pathways included myosin light chain kinase, MAP kinase, profilin 2, fibroblast growth factor receptor, integrin b4, and p21-activated kinase.

Conclusion

Circadian rhythm disruption results in exacerbated immune response and dysregulated expression of cytoskeletal genes involved in the regulation of epithelial and vascular barrier integrity-the mechanistic underpinnings of acute lung injury. Further studies need to explore circadian disorganization as a druggable target.

DNALI1 interacts with the MEIG1/PACRG complex within the manchette and is required for proper sperm flagellum assembly in mice

The manchette is a transient and unique structure present in elongating spermatids and required for proper differentiation of the germ cells during spermatogenesis. Previous work indicated that the MEIG1/PACRG complex locates in the manchette and is involved in the transport of cargos, such as SPAG16L, to build the sperm flagellum. Here, using co-immunoprecipitation and pull-down approaches in various cell systems, we established that DNALI1, an axonemal component originally cloned from Chlamydomonas reinhardtii, recruits and stabilizes PACRG and we confirm in vivo, the co-localization of DNALI1 and PACRG in the manchette by immunofluorescence of elongating murine spermatids. We next generated mice with a specific deficiency of DNALI1 in male germ cells, and observed a dramatic reduction of the sperm cells, which results in male infertility. In addition, we observed that the majority of the sperm cells exhibited abnormal morphology including misshapen heads, bent tails, enlarged midpiece, discontinuous accessory structure, emphasizing the importance of DNALI1 in sperm differentiation. Examination of testis histology confirmed impaired spermiogenesis in the mutant mice. Importantly, while testicular levels of MEIG1, PACRG, and SPAG16L proteins were unchanged in the Dnali1 mutant mice, their localization within the manchette was greatly affected, indicating that DNALI1 is required for the formation of the MEIG1/PACRG complex within the manchette. Interestingly, in contrast to MEIG1 and PACRG-deficient mice, the DNALI1-deficient mice also showed impaired sperm spermiation/individualization, suggesting additional functions beyond its involvement in the manchette structure. Overall, our work identifies DNALI1 as a protein required for sperm development.

T-complex-associated-testis-expressed 3 (TCTE3) is a novel marker for pancreatobiliary carcinomas

Several markers of pancreatobiliary lineage have been described in the literature. However, none have demonstrated sufficient specificity and sensitivity to warrant diagnostic use. We evaluated the utility of T-complex-associated-testis-expressed 3 (TCTE3) as a pancreatobiliary marker. A set of 247 adenocarcinomas from the gastrointestinal (GI) tract was identified including 18 from the gastroesophageal junction (GEJ), 29 stomach, 17 ampullary, 62 pancreatic, and 16 common bile duct and gallbladder (CBD/GB), 13 non-ampullary small intestine, 32 colon, and 24 rectum. The remainder consisted of 16 cholangiocarcinomas and 20 hepatocellular carcinomas (HCC). Additionally, 163 adenocarcinomas from the breast, gynecologic tract, prostate, urothelium, kidney, and lung were stained for comparison. Immunohistochemistry for TCTE3 and other gastrointestinal markers was performed. Positive expression of TCTE3 was characterized by a strong, well-defined membranous pattern with or without weak cytoplasmic staining. Expression was identified in the normal epithelial cells of pancreatobiliary tree, but staining was absent in normal epithelial cells of esophagus, stomach, and intestine. Hepatocytes, pancreatic acini and islets and other non-epithelial cells were also negative for staining. TCTE3 was expressed in 93.5% of pancreatic ductal adenocarcinomas, 37.5% of CBD/GB adenocarcinomas, 50% of cholangiocarcinomas, 76.4% of ampullary adenocarcinomas, and 33.3% of GEJ adenocarcinomas. Only 3.5% of the gastric, 7.7% of non-ampullary small intestinal and 6.25% of colonic tumors exhibited positive staining. Expression was absent in rectal carcinomas and HCCs. These results suggest that TCTE3 is a useful marker of pancreatobiliary differentiation and may aid in distinguishing these tumors from gastric and intestinal primary tumors.

Promoter targeted bisulfite sequencing reveals DNA methylation profiles associated with low sperm motility in asthenozoospermia

STUDY QUESTION

Is there an association between sperm DNA methylation profiles and asthenozoospermia?

SUMMARY ANSWER

DNA methylation, at specific CpGs but not at the global level, was significantly different between low motile sperm cells of asthenozoospermic individuals and high motile sperm cells of normozoospermic controls.

WHAT IS KNOWN ALREADY

Aberrant DNA methylation, both globally and restricted to a specific gene locus, has been associated with male infertility and abnormal semen parameters.

STUDY DESIGN, SIZE, DURATION

This was a case-control study investigating the differences in DNA methylation at CpGs in promoter regions between high and low motile sperm cells from eight normozoospermic controls and seven asthenozoospermic patients.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The liquid hybridization capture-based bisulfite sequencing method was used to determine DNA methylation at CpGs in promoter regions. The global inter-individual and intra-individual methylation variability were estimated by evaluating the methylation variance between and within different motile sperm fractions from the same or different individuals. Asthenozoospermia-associated differentially methylated or variable CpGs and differentially methylated regions were identified by comparing the DNA methylation of high motile sperm cells from normozoospermic controls with that of low motile sperm cells from asthenozoospermic patients.

MAIN RESULTS AND THE ROLE OF CHANCE

In this study, we determined the global DNA methylation level (24.7%), inter-individual variance (14.4%) and intra-individual differences between high and low motile sperm fractions (3.9%). We demonstrated that there were no statistically significant differences in either the global DNA methylation level or global methylation variability between sperm from men with normozoospermia or asthenozoospermia. Between high motile sperm from men with normozoospermia and low motile sperm from men with asthenozoospermia, we identified 134 differentially methylated CpGs, 41 differentially methylated regions and 134 differentially variable CpGs. The genomic distribution patterns of the differential methylation spectrum suggested that gene expression may be affected in low motile sperm cells of asthenozoospermic patients. Finally, through a functional analysis, we detected 16 differentially methylated or variable genes that are required for spermatogenesis and sperm motility or dominantly expressed in testis.

LIMITATIONS, REASONS FOR CAUTION

The sample size in this study was limited, although the participants in the two groups were carefully selected and well matched. Our results must be verified in larger cohorts with the use of different techniques. Furthermore, our results were descriptive, and follow-up studies will be needed to elucidate the effect of differential methylation profiles on asthenozoospermia.

WIDER IMPLICATIONS OF THE FINDINGS

Our study identified asthenozoospermia-associated DNA methylation profiles and proposed a list of genes, which were suggested to be involved in the regulation of sperm motility through an alteration of DNA methylation. These results will provide promising clues for understanding the effect of DNA methylation on sperm motility and asthenozoospermia.

STUDY FUNDING/COMPETING INTERESTS

This study was funded primarily by the National Natural Science Foundation of China, Shenzhen Project of Science and Technology and the National Basic Research Program of China. The authors have no competing interests.

Disruption of murine Tcte3-3 induces tissue specific apoptosis via co-expression of Anxa5 and Pebp1

Programmed cell death or apoptosis plays a vital physiological role in the development and homeostasis. Any discrepancy in apoptosis may trigger testicular and neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. Tcte3 (T-complex testis expressed 3) is an accessory component of axonemal and cytoplasmic dynein which expresses predominantly in meiotic and postmeiotic germ cells. It plays an essential role during spermatogenesis; however, to explore its diverse and complex functioning in male germ cell apoptosis, requires further prosecution. Here, 2D-gel electrophoresis, mass spectrometry and qRT-PCR analyses were performed to elucidate the differential expression of genes, in both wild-type and homozygous Tcte3-3 mice. We observed an increased expression of Tcte3 in homozygotes as compared to wild-type testes. Perpetually, an increased expression of Anxa5 and Pebp1, while a lower expression of Rsph1 was detected in Tcte3-3^-/- mice. We propose that over-expression of Pebp1 and Anxa5 in Tcte3-3^-/- testes might be due to increased apoptosis. To evaluate this possibility, testes specific microarray data set extracted from NCBI gene ontology omnibus (GEO) was used to cluster the possible co-expression partners of Tcte3. Further functional coherence of compiled candidate genes was monitored computationally by studying the common TFBS overlapped at the regulatory regions. Differential expression of Tcte3-3 and its involvement in apoptosis may provide a basis for the investigation of transcriptional specificities of other Tcte3 paralogs (Tcte3-1 and Tcte3-2). A complete understanding of controlling factors which have implications in regulating tissue-specific Tcte3 expression would provide additional insights into the gene control events. The collective knowledge may prove useful for the development of novel therapeutic regimen and would open new avenues in defining selective roles of Tcte3 in germ cell development.

Management of primary ciliary dyskinesia/Kartagener's syndrome in infertile male patients and current progress in defining the underlying genetic mechanism

Kartagener's syndrome (KS) is an autosomal recessive genetic disease accounting for approximately 50% of the cases of primary ciliary dyskinesia (PCD). As it is accompanied by many complications, PCD/KS severely affects the patient's quality of life. Therapeutic approaches for PCD/KS aim to enhance prevention, facilitate rapid definitive diagnosis, avoid misdiagnosis, maintain active treatment, control infection and postpone the development of lesions. In male patients, sperm flagella may show impairment in or complete absence of the ability to swing, which ultimately results in male infertility. Assisted reproductive technology will certainly benefit such patients. For PCD/KS patients with completely immotile sperm, intracytoplasmic sperm injection may be very important and even indispensable. Considering the number of PCD/KS susceptibility genes and mutations that are being identified, more extensive genetic screening is indispensable in patients with these diseases. Moreover, further studies into the potential molecular mechanisms of these diseases are required. In this review, we summarize the available information on various aspects of this disease in order to delineate the therapeutic objectives more clearly, and clarify the efficacy of assisted reproductive technology as a means of treatment for patients with PCD/KS-associated infertility.

Periventricular heterotopia in 6q terminal deletion syndrome: role of the C6orf70 gene

Periventricular nodular heterotopia is caused by defective neuronal migration that results in heterotopic neuronal nodules lining the lateral ventricles. Mutations in filamin A (FLNA) or ADP-ribosylation factor guanine nucleotide-exchange factor 2 (ARFGEF2) cause periventricular nodular heterotopia, but most patients with this malformation do not have a known aetiology. Using comparative genomic hybridization, we identified 12 patients with developmental brain abnormalities, variably combining periventricular nodular heterotopia, corpus callosum dysgenesis, colpocephaly, cerebellar hypoplasia and polymicrogyria, harbouring a common 1.2 Mb minimal critical deletion in 6q27. These anatomic features were mainly associated with epilepsy, ataxia and cognitive impairment. Using whole exome sequencing in 14 patients with isolated periventricular nodular heterotopia but no copy number variants, we identified one patient with periventricular nodular heterotopia, developmental delay and epilepsy and a de novo missense mutation in the chromosome 6 open reading frame 70 (C6orf70) gene, mapping in the minimal critical deleted region. Using immunohistochemistry and western blots, we demonstrated that in human cell lines, C6orf70 shows primarily a cytoplasmic vesicular puncta-like distribution and that the mutation affects its stability and subcellular distribution. We also performed in utero silencing of C6orf70 and of Phf10 and Dll1, the two additional genes mapping in the 6q27 minimal critical deleted region that are expressed in human and rodent brain. Silencing of C6orf70 in the developing rat neocortex produced periventricular nodular heterotopia that was rescued by concomitant expression of wild-type human C6orf70 protein. Silencing of the contiguous Phf10 or Dll1 genes only produced slightly delayed migration but not periventricular nodular heterotopia. The complex brain phenotype observed in the 6q terminal deletion syndrome likely results from the combined haploinsufficiency of contiguous genes mapping to a small 1.2 Mb region. Our data suggest that, of the genes within this minimal critical region, C6orf70 plays a major role in the control of neuronal migration and its haploinsufficiency or mutation causes periventricular nodular heterotopia.

Identification of TCTE3 as a gene responsible for congenital diaphragmatic hernia using a high-resolution single-nucleotide polymorphism array

PURPOSE

Congenital diaphragmatic hernia (CDH) is a birth defect of the diaphragm associated with pulmonary hypoplasia. Although genetic factors have been suggested to play a role, the etiology of CDH is still largely unknown. In this study, we analyzed copy number variants (CNVs) using a single-nucleotide polymorphism (SNP) array to examine whether microdeletions contribute to the pathogenesis of this disease.

METHODS

A total of 28 CDH patients, including 24 isolated and 4 non-isolated cases, were available. We performed CNV analysis using high-resolution SNP arrays (370K, 550K, 660K; Illumina Inc.) and CNstream software. Deletions in loci that have been suggested in previous studies to contain candidate genes affecting CDH were analyzed.

RESULTS

We detected 335, 6 and 133 deletions specific for patients in 14 (350K array), 3 (550K) and 11 (660K) cases, respectively. Among these deletions, no segments included the previously suggested candidate genes with the exception of an 18-kb deletion observed in the candidate locus 6q27 in two non-isolated patients. This deleted region contains exon 4 of the t-complex-associated-testis-expressed 3 (TCTE3) gene.

CONCLUSION

Because TCTE3 encodes a putative light chain of the outer dynein arm of cilia and human diseases caused by ciliary dysfunction show various phenotypes including skeletal defect, TCTE3 may be a genetic candidate influencing CDH.

Disruption of the murine dynein light chain gene Tcte3-3 results in asthenozoospermia

To elucidate the role of the mouse gene Tcte3 (Tctex2), which encodes a putative light chain of the outer dynein arm of cilia and sperm flagella, we have inactivated this gene in mice using targeted disruption. Breeding of heterozygous males and females resulted in normal litter size; however, we were not able to detect homozygous Tcte3-deficent mice using standard genotype techniques. In fact, our results indicate the presence of at least three highly similar copies of the Tcte3 gene (Tcte3-1, Tcte3-2, and Tcte3-3) in the murine genome. Therefore, quantitative real-time PCR was established to differentiate between mice having one or two targeted Tcte3-3 alleles. By this approach, Tcte3-3(-/-) animals were identified, which were viable and revealed no obvious malformation. Interestingly, some homozygous Tcte3-3-deficient male mice bred with wild-type female produced no offspring while other Tcte3-3-deficient males revealed decreased sperm motility but were fertile. In infertile Tcte3-3(-/-) males, spermatogenesis was affected and sperm motility was reduced, too, resulting in decreased ability of Tcte3-3-deficient spermatozoa to move from the uterus into the oviduct. Impaired flagellar motility is not correlated with any gross defects in the axonemal structure, since outer dynein arms are detectable in sperm of Tcte3-3(-/-) males. However, in infertile males, deficient Tcte3-3 function is correlated with increased apoptosis during male germ cell development, resulting in a reduction of sperm number. Moreover, multiple malformations in developing haploid germ cells are present. Our results support a role of Tcte3-3 in generation of sperm motility as well as in male germ cell differentiation.

Clinical and genetic aspects of primary ciliary dyskinesia/Kartagener syndrome

Primary ciliary dyskinesia is a genetically heterogeneous disorder of motile cilia. Most of the disease-causing mutations identified to date involve the heavy (dynein axonemal heavy chain 5) or intermediate(dynein axonemal intermediate chain 1) chain dynein genes in ciliary outer dynein arms, although a few mutations have been noted in other genes. Clinical molecular genetic testing for primary ciliary dyskinesia is available for the most common mutations. The respiratory manifestations of primary ciliary dyskinesia (chronic bronchitis leading to bronchiectasis, chronic rhino-sinusitis, and chronic otitis media)reflect impaired mucociliary clearance owing to defective axonemal structure. Ciliary ultrastructural analysis in most patients (>80%) reveals defective dynein arms, although defects in other axonemal components have also been observed. Approximately 50% of patients with primary ciliary dyskinesia have laterality defects (including situs inversus totalis and, less commonly, heterotaxy, and congenital heart disease),reflecting dysfunction of embryological nodal cilia. Male infertility is common and reflects defects in sperm tail axonemes. Most patients with primary ciliary dyskinesia have a history of neonatal respiratory distress, suggesting that motile cilia play a role in fluid clearance during the transition from a fetal to neonatal lung. Ciliopathies involving sensory cilia, including autosomal dominant or recessive polycystic kidney disease, Bardet-Biedl syndrome, and Alstrom syndrome, may have chronic respiratory symptoms and even bronchiectasis suggesting clinical overlap with primary ciliary dyskinesia.

Primary ciliary dyskinesia associated with normal axoneme ultrastructure is caused by DNAH11 mutations

Primary ciliary dyskinesia (PCD) is an inherited disorder characterized by perturbed or absent beating of motile cilia, which is referred to as Kartagener syndrome (KS) when associated with situs inversus. We present a German family in which five individuals have PCD and one has KS. PCD was confirmed by analysis of native and cultured respiratory ciliated epithelia with high-speed video microscopy. Respiratory ciliated cells from the affected individuals showed an abnormal nonflexible beating pattern with a reduced cilium bending capacity and a hyperkinetic beat. Interestingly, the axonemal ultrastructure of these respiratory cilia was normal and outer dynein arms were intact, as shown by electron microscopy and immunohistochemistry. Microsatellite analysis indicated genetic linkage to the dynein heavy chain DNAH11 on chromosome 7p21. All affected individuals carried the compound heterozygous DNAH11 mutations c.12384C>G and c.13552_13608del. Both mutations are located in the C-terminal domain and predict a truncated DNAH11 protein (p.Y4128X, p.A4518_A4523delinsQ). The mutations described here were not present in a cohort of 96 PCD patients. In conclusion, our findings support the view that DNAH11 mutations indeed cause PCD and KS, and that the reported DNAH11 nonsense mutations are associated with a normal axonemal ultrastructure and are compatible with normal male fertility.

Genetic causes of bronchiectasis: primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder reflecting abnormalities in the structure and function of motile cilia and flagella, causing impairment of mucociliary clearance, left-right body asymmetry, and sperm motility. Clinical manifestations include respiratory distress in term neonates, recurrent otosinopulmonary infections, bronchiectasis, situs inversus and/or heterotaxy, and male infertility. Genetic discoveries are emerging from family-based linkage studies and from testing candidate genes. Mutations in 2 genes, DNAI1 and DNAH5, frequently cause PCD as an autosomal recessive disorder. A clinical genetic test has been recently established for DNAI1 and DNAH5, which involves sequencing 9 exons that harbor the most common mutations. This approach will identify at least one mutation in these 2 genes in approximately 25% of PCD patients. If biallelic mutations are identified, the test is diagnostic. If only one mutation is identified, the full gene may be sequenced to search for a trans-allelic mutation. As more disease-causing gene mutations are identified, broader genetic screening panels will further identify patients with PCD. Ongoing investigations are beginning to identify genetic mutations in novel clinical phenotypes for PCD, such as congenital heart disease and male infertility, and new associations are being established between 'ciliary' genetic mutations and clinical phenotypes.

Genetic defects in ciliary structure and function

Cilia, hair-like structures extending from the cell membrane, perform diverse biological functions. Primary (genetic) defects in the structure and function of sensory and motile cilia result in multiple ciliopathies. The most prominent genetic abnormality involving motile cilia (and the respiratory tract) is primary ciliary dyskinesia (PCD). PCD is a rare, usually autosomal recessive, genetically heterogeneous disorder characterized by sino-pulmonary disease, laterality defects, and male infertility. Ciliary ultrastructural defects are identified in approximately 90% of PCD patients and involve the outer dynein arms, inner dynein arms, or both. Diagnosing PCD is challenging and requires a compatible clinical phenotype together with tests such as ciliary ultrastructural analysis, immunofluorescent staining, ciliary beat assessment, and/or nasal nitric oxide measurements. Recent mutational analysis demonstrated that 38% of PCD patients carry mutations of the dynein genes DNAI1 and DNAH5. Increased understanding of the pathogenesis will aid in better diagnosis and treatment of PCD.

A common variant in combination with a nonsense mutation in a member of the thioredoxin family causes primary ciliary dyskinesia

Thioredoxins belong to a large family of enzymatic proteins that function as general protein disulfide reductases, therefore participating in several cellular processes via redox-mediated reactions. So far, none of the 18 members of this family has been involved in human pathology. Here we identified TXNDC3, which encodes a thioredoxin-nucleoside diphosphate kinase, as a gene implicated in primary ciliary dyskinesia (PCD), a genetic condition characterized by chronic respiratory tract infections, left-right asymmetry randomization, and male infertility. We show that the disease, which segregates as a recessive trait, results from the unusual combination of the following two transallelic defects: a nonsense mutation and a common intronic variant found in 1% of control chromosomes. This variant affects the ratio of two physiological TXNDC3 transcripts: the full-length isoform and a novel isoform, TXNDC3d7, carrying an in-frame deletion of exon 7. In vivo and in vitro expression data unveiled the physiological importance of TXNDC3d7 (whose expression was reduced in the patient) and the corresponding protein that was shown to bind microtubules. PCD is known to result from defects of the axoneme, an organelle common to respiratory cilia, embryonic nodal cilia, and sperm flagella, containing dynein arms, with, to date, the implication of genes encoding dynein proteins. Our findings, which identify a another class of molecules involved in PCD, disclose the key role of TXNDC3 in ciliary function; they also point to an unusual mechanism underlying a Mendelian disorder, which is an SNP-induced modification of the ratio of two physiological isoforms generated by alternative splicing.

The murine Dnali1 gene encodes a flagellar protein that interacts with the cytoplasmic dynein heavy chain 1

Axonemal dyneins are large motor protein complexes generating the force for the movement of eukaryotic cilia and flagella. Disruption of axonemal dynein function leads to loss of ciliary motility and can result in male infertility or lateralization defects. Here, we report the molecular analysis of a murine gene encoding the dynein axonemal light intermediate chain Dnali1. The Dnali1 gene is localized on chromosome 4 and consists of six exons. It is predominantly expressed within the testis but at a lower level Dnali1 transcripts were also observed in different murine tissues, which exhibit cilia. Two transcript variants were detected, generated by the usage of two alternative polyadenylation signals within exon 6. Antibodies were raised against a GST-Dnali1 fusion protein and used to localize Dnali1 within differentiating male germ cells. Dnali1 is strongly expressed in spermatids but was also detected in spermatocytes. Moreover, the Dnali1 protein was localized in cilia of the trachea as well as in flagella of mature sperm supporting its function as an axonemal dynein. To identify putative Dnali1 interacting polypeptides, a yeast two-hybrid approach was performed using a murine testicular cDNA library. By this assay, the C-terminal part of the cytoplasmic dynein heavy chain 1 was identified as a putative interacting polypeptide of Dnali1. The interaction between the axonemal and the cytoplasmic dynein fragments was proven by co-immuno and co-localization experiments.

Genetic analysis of the cytoplasmic dynein subunit families

Cytoplasmic dyneins, the principal microtubule minus-end-directed motor proteins of the cell, are involved in many essential cellular processes. The major form of this enzyme is a complex of at least six protein subunits, and in mammals all but one of the subunits are encoded by at least two genes. Here we review current knowledge concerning the subunits, their interactions, and their functional roles as derived from biochemical and genetic analyses. We also carried out extensive database searches to look for new genes and to clarify anomalies in the databases. Our analysis documents evolutionary relationships among the dynein subunits of mammals and other model organisms, and sheds new light on the role of this diverse group of proteins, highlighting the existence of two cytoplasmic dynein complexes with distinct cellular roles.

Identification of predicted human outer dynein arm genes: candidates for primary ciliary dyskinesia genes

BACKGROUND

Primary ciliary dyskinesia (PCD) is a severe inherited disorder characterised by chronic respiratory disease, male infertility, and, in approximately 50% of affected individuals, a left-right asymmetry defect called situs inversus. PCD is caused by defects in substructures of the ciliary and flagellar axoneme, most commonly loss of the outer dynein arms. Although PCD is believed to involve mutations in many genes, only three have been identified.

METHODS

To facilitate discovery of new PCD genes, we have used database searching and analysis to systematically identify the human homologues of proteins associated with the Chlamydomonas reinhardtii outer dynein arm, the best characterised outer arm of any species.

RESULTS

We find that 12 out of 14 known Chlamydomonas outer arm subunits have one or more likely orthologues in humans. The results predict a total of 24 human genes likely to encode outer dynein arm subunits and associated proteins possibly necessary for outer arm assembly, plus 12 additional closely related human genes likely to encode inner dynein arm subunits.

CONCLUSION

These genes, which have been located on the human chromosomes for easy comparison with known or suspected PCD loci, are excellent candidates for screening for disease-causing mutations in PCD patients with outer and/or inner dynein arm defects.

[The respiratory mucociliary system and its exploration in primary ciliary dyskinesia]

BACKGROUND

We analyzed the main characteristic features of the respiratory epithelium mucociliary system and the different tests of ciliary beat and mucociliary transport (mucociliary clearance). This knowledge is necessary for an often interdisciplinary diagnosis and treatment of primary ciliary dyskinesia.

METHODS

Review of the literature and personal experience of the different tests of ciliary structure and function.

RESULTS

This disease is characterized by abnormalities in ciliary structure/function. The genetic mechanisms and the ultrastructural abnormalities that are involved are heterogenous compared to the relative homogeneity of the clinical presentation.

CONCLUSION

The diagnostic criteria are compatible clinical features (chronic upper airway and bronchopulmonary infections, situs inversus...) coupled with tests of ciliary structure and function.

Identification and analysis of axonemal dynein light chain 1 in primary ciliary dyskinesia patients

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder characterized by chronic infections of the upper and lower airways, randomization of left/right body asymmetry, and reduced fertility. The phenotype results from dysfunction of motile cilia of the respiratory epithelium, at the embryonic node and of sperm flagella. Ultrastructural defects often involve outer dynein arms (ODAs), that are composed of several light (LCs), intermediate, and heavy (HCs) dynein chains. We recently showed that recessive mutations of DNAH5, the human ortholog of the biflagellate Chlamydomonas ODA gamma-HC, cause PCD. In Chlamydomonas, motor protein activity of the gamma-ODA-HC is regulated by binding of the axonemal LC1. We report the identification of the human (DNAL1) and murine (Dnal1) orthologs of the Chlamydomonas LC1-gene. Northern blot and in situ hybridization analyses revealed specific expression in testis, embryonic node, respiratory epithelium, and ependyma, resembling the DNAH5 expression pattern. In silico protein analysis showed complete conservation of the LC1/gamma-HC binding motif in DNAL1. Protein interaction studies demonstrated binding of DNAL1 and DNAH5. Based on these findings, we considered DNAL1 a candidate for PCD and sequenced all exons of DNAL1 in 86 patients. Mutational analysis was negative, excluding a major role of DNAL1 in the pathogenesis of PCD.

Primary ciliary dyskinesia: clinical presentation, diagnosis and genetics

Primary ciliary dyskinesia (PCD) is a phenotypically and genetically heterogeneous disorder with an autosomal-recessive inheritance pattern. Only rarely other modes of inheritance such as X-linked transmission are observed. The disease phenotype is caused by defects of respiratory cilia, sperm tails and the cilia of the embryonic node. The lack of mucociliary clearance contributes to recurrent respiratory tract infections, that might progress to permanent lung damage (bronchiectasis). The goal of therapy is prevention of bronchiectasis. Male infertility due to sperm tail dysmotility is another frequent finding in PCD. Half of affected individuals have situs inversus (Kartagener's syndrome) due to randomization of left/right body asymmetry. Currently three genes (DNAI1, DNAH5, DNAH11) that encode for dynein proteins have been linked to recessive PCD. Mutations in RPGR located on the X chromosome have been identified in males with retinitis pigmentosa and PCD. As a screening test nasal nitric oxide (NO) measurement is widely used. Establishment of diagnosis currently relies on electron microscopy, direct evaluation of ciliary beat by light microscopy, and/or the novel method of high-resolution immunofluorecent analysis of respiratory cilia.

Mutations in a Novel Locus on Mouse Chromosome 11 Resulting in Male Infertility Associated with Defects in Microtubule Assembly and Sperm Tail Function1

Traditional gene knock-out approaches using homologous recombination in embryonic stem cells are routinely used to provide functional information about genes involved in reproduction. In the present study, we examined a novel approach using N-ethyl-N-nitrosourea (ENU) together with a balancer chromosome mating strategy to identify new loci with functional roles in male fertility. Our genetic strategy is a forward-genetic approach; thus, our phenotypic investigation begins with the discovery of an abnormal phenotype without previous knowledge of the mutant locus. We isolated eight recessive mutations on chromosome 11 that resulted in male or female infertility from a screen of 184 founder pedigrees from ENU-treated males. After testing the six male infertile and two female infertile mutations for their ability to complement, we found that three independent recessive male infertile mutations failed to complement each other. The male infertility was associated with reduced epididymal sperm count, a block in late-spermatid differentiation, and increased apoptosis. Furthermore, the three male infertile mutants had severe defects in epididymal sperm morphology associated with incorrect microtubule assembly. Electron microscopy revealed unique defects in sperm head and tail morphology for each of the three alleles. One allele had an abnormal manchette assembly of the sperm head. The other two alleles had different abnormalities in the 9+2 patterning of the microtubules in the sperm tail axoneme, with one containing only five of the microtubule doublets and the other containing an extra doublet. The isolation of this allelic series identifies a new locus on mouse chromosome 11 that is required for spermiogenesis and male fertility.

Transmission Ratio Distortion in Mice

The most studied example of transmission ratio distortion (TRD) in mice is that of the t-complex. This is a variant region of Chromosome 17 which exists as a polymorphism in wild mice. Males heterozygous for a t-haplotype and a normal Chr 17 transmit the t-haplotype to >50% of their young, up to 99%. Homozygous males are sterile. The TRD produced by the t-complex is due to the action of three or more distorter genes (Tcd) on a responder gene (Tcr). t-Haplotypes are maintained intact by crossover suppression induced by four neighboring inversions, the Tcd and Tcr loci lying in different inversions. Sperm formation is normal in t/t males, but sperm function is impaired through gross defects in sperm motility. The responder gene has been identified as a fusion gene formed from a sperm motility kinase and a ribosomal S6 kinase. Three candidate distorter genes have also been identified as genes coding for dynein chains, and thus possibly involved in sperm flagellar function.