Characterization of a novel human dynein-related gene that is specifically expressed in testis

Sperm defects in primary ciliary dyskinesia and related causes of male infertility

The core axoneme structure of both the motile cilium and sperm tail has the same ultrastructural 9 + 2 microtubular arrangement. Thus, it can be expected that genetic defects in motile cilia also have an effect on sperm tail formation. However, recent studies in human patients, animal models and model organisms have indicated that there are differences in components of specific structures within the cilia and sperm tail axonemes. Primary ciliary dyskinesia (PCD) is a genetic disease with symptoms caused by malfunction of motile cilia such as chronic nasal discharge, ear, nose and chest infections and pulmonary disease (bronchiectasis). Half of the patients also have situs inversus and in many cases male infertility has been reported. PCD genes have a role in motile cilia biogenesis, structure and function. To date mutations in over 40 genes have been identified cause PCD, but the exact effect of these mutations on spermatogenesis is poorly understood. Furthermore, mutations in several additional axonemal genes have recently been identified to cause a sperm-specific phenotype, termed multiple morphological abnormalities of the sperm flagella (MMAF). In this review, we discuss the association of PCD genes and other axonemal genes with male infertility, drawing particular attention to possible differences between their functions in motile cilia and sperm tails.

Characterization and genomic structure of Dnah9, and its roles in nodal signaling pathways in the Japanese flounder (Paralichthys olivaceus)

The nodal signaling pathway has been shown to play crucial roles in inducing and patterning the mesoderm and endoderm, as well as in regulating neurogenesis and left-right axis asymmetry. Here, we present the first complete cDNA and genomic sequences as well as the promoter predication of the Dnah9 gene in the Japanese flounder. The 15,558-bp-long cDNA is divided into 96 exons and spread over 138 kb of genomic DNA. Protein sequence comparison showed that it shares higher identity with other vertebrate orthologs, with an ATP binding dynein motor, AAA domain and microtubule binding stalk of dynein motor. Dnah9 exhibited maternal and ubiquitous expression in all cells of the early development stages, but became concentrated in the head at 1 DAH, as identified by qRT-PCR and in situ hybridization methods. Furthermore, after nodal signaling was inhibited, the level of Southpaw did not change significantly at early development stage (50 % epiboly) but increased significantly at late stages (27-somite stages and 1 DAH), as well as the expression of Lefty, an inhibitor of nodal signaling, increased continuously. On the other hand, the expression level of Dnah9 decreased. The transcription factor binding site of FAST-1 (SMAD interacting protein) was identified in the transcription region of Dnah9 by the promoter analysis, which might format the complexes of SMADs, FAST-1 and the transcription region of Dnah9 served as a bridge of Dnah9 and nodal signaling. All evidences indicated that Dnah9 might be downstream of nodal during the early development stages, and an indirect function through SMADs for nodal signaling pathway.

Analysis of the basal chordate Botryllus schlosseri reveals a set of genes associated with fertility

Background

Gonad differentiation is an essential function for all sexually reproducing species, and many aspects of these developmental processes are highly conserved among the metazoa. The colonial ascidian, Botryllus schlosseri is a chordate model organism which offers two unique traits that can be utilized to characterize the genes underlying germline development: a colonial life history and variable fertility. These properties allow individual genotypes to be isolated at different stages of fertility and gene expression can be characterized comprehensively.

Results

Here we characterized the transcriptome of both fertile and infertile colonies throughout blastogenesis (asexual development) using differential expression analysis. We identified genes (as few as 7 and as many as 647) regulating fertility in Botryllus at each stage of blastogenesis. Several of these genes appear to drive gonad maturation, as they are expressed by follicle cells surrounding both testis and oocyte precursors. Spatial and temporal expression of differentially expressed genes was analyzed by in situ hybridization, confirming expression in developing gonads.

Conclusion

We have identified several genes expressed in developing and mature gonads in B. schlosseri. Analysis of genes upregulated in fertile animals suggests a high level of conservation of the mechanisms regulating fertility between basal chordates and vertebrates.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1183) contains supplementary material, which is available to authorized users.

Antisense and Short Hairpin RNA (shRNA) Constructs Targeting PIN (Protein Inhibitor of NOS) Ameliorate Aging-Related Erectile Dysfunction in the Rat

INTRODUCTION

Over-expression of penile neuronal nitric oxide synthase (PnNOS) from a plasmid ameliorates aging-related erectile dysfunction (ED), whereas over-expression of the protein inhibitor of NOS (PIN), that binds to nNOS, increases ED.

AIM

To improve this form of gene therapy for ED by comparing the electrical field response of short hairpin RNA (shRNA) for PIN with that of antisense PIN RNA.

MAIN OUTCOME MEASURE

Both shRNA and antisense RNA gene therapy vectors increased intracavernosal pressure in aged rats.

METHODS

PIN small interfering RNA (siRNA), and plasmid constructs for cytomegalovirus promoter plasmid vector (pCMV-PIN), pCMV-PIN antisense RNA, pSilencer2.1-U6-PIN-shRNA; and pSilencer2.1-U6-randomer-shRNA were prepared and validated by transfection into HEK293 cells, determining the effects on PIN expression by Western blot. Plasmid constructs were then injected, followed by electroporation, into the penile corpora cavernosa of aged (20-month-old) Fisher 344 rats and, 1 month later, the erectile response was measured by intracavernosal pressure increase following electrical field stimulation (EFS) of the cavernosal nerve. PIN was estimated in penile tissue by Western blot and real-time reverse transcriptase-polymerase chain reaction. Cyclic guanosine monophosphate (cGMP) measurements were conducted by competitive enzyme immunoassay (EIA). Immunohistofluorescence detected PIN in corporal tissue sections.

RESULTS

In cell culture, PIN siRNA and plasmid-expressed pU6-PIN-shRNA effectively reduced PIN expression from pCMV-PIN. pSilencer2.1-U6-PIN-shRNA corrected the impaired erectile response to EFS in aged rats and raised it above the value for young rats, more efficiently than pCMV-PIN antisense RNA. PIN mRNA expression in the penis was decreased by >70% by the shRNA but remained unaffected by the antisense RNA, whereas PIN protein expression was reduced in both cases, particularly in the dorsal nerve. PIN antisense increased cGMP concentration in treated tissue by twofold.

CONCLUSION

pSilencer2.1-U6-PIN-shRNA gene therapy was more effective than the antisense PIN mRNA in ameliorating ED in the aged rat, thereby suggesting that PIN is indeed a physiological inhibitor of nNOS and nitrergic neurotransmission in the penis.

Axonemal dynein expression in human fetal tracheal epithelium

Ciliogenesis in human fetal airway epithelium occurs from 11 to 24 gestational weeks. Using genetic and antigenic markers specific for human axonemal dynein heavy chain 9, we characterized temporal aspects of axonemal dynein expression associated with large airway epithelial ciliogenesis during human fetal development. Late in the first trimester, an undifferentiated columnar epithelium is characteristic of the large airways, and immunocytochemical studies exhibited focal localization of axonemal dynein antigen on luminal epithelial cell borders at sites consistent with emergent ciliary beds. From 12 to 22 wk, immunocytochemical labeling of new ciliary beds was prominent, and localization within the cytoplasm of epithelial cells suggested avid synthesis of axonemal dynein in advance of ciliogenic events. Quantitative RT-PCR of tracheal RNA and in situ hybridization studies compared favorably with immunocytochemical findings with the earliest expression of axonemal dynein at 9-10 wk gestation. These studies have documented that axonemal dynein is expressed early in human fetal life during airway epithelial maturation and well before histological or ultrastructural evidence of ciliogenesis is apparent.

Sptrx-2, a fusion protein composed of one thioredoxin and three tandemly repeated NDP-kinase domains is expressed in human testis germ cells

BACKGROUND

Thioredoxins (Trx) are small redox proteins that function as general protein disulphide reductases and regulate several cellular processes such as transcription factor DNA binding activity, apoptosis and DNA synthesis. In mammalian organisms, thioredoxins are generally ubiquitously expressed in all tissues, with the exception of Sptrx-1 which is specifically expressed in sperm cells.

RESULTS

We report here the identification and characterization of a novel member of the thioredoxin family, the second with a tissue-specific distribution in human sperm, termed Sptrx-2. The Sptrx-2 ORF (open reading frame) encodes for a protein of 588 amino acids with two different domains: an N-terminal thioredoxin domain encompassing the first 105 residues and a C-terminal domain composed of three repeats of a NDP kinase domain. The Sptrx-2 gene spans about 51 kb organized in 17 exons and maps at locus 7p13-14. Sptrx-2 mRNA is exclusively expressed in human testis, mainly in primary spermatocytes, while Sptrx-2 protein expression is detected from the pachytene spermatocytes stage onwards, peaking at round spermatids stage. Recombinant full-length Sptrx-2 expressed in bacteria displayed neither thioredoxin nor NDP kinase enzymatic activity.

CONCLUSIONS

The sperm specific expression of Sptrx-2, together with its chromosomal assignment to a position reported as a potential locus for flagellar anomalies and male infertility phenotypes such as primary ciliary dyskinesia, suggests that it might be a novel component of the human sperm axonemal organization.

Axonemal dynein intermediate-chain gene (DNAI1) mutations result in situs inversus and primary ciliary dyskinesia (Kartagener syndrome)

Kartagener syndrome (KS) is a trilogy of symptoms (nasal polyps, bronchiectasis, and situs inversus totalis) that is associated with ultrastructural anomalies of cilia of epithelial cells covering the upper and lower respiratory tracts and spermatozoa flagellae. The axonemal dynein intermediate-chain gene 1 (DNAI1), which has been demonstrated to be responsible for a case of primary ciliary dyskinesia (PCD) without situs inversus, was screened for mutation in a series of 34 patients with KS. We identified compound heterozygous DNAI1 gene defects in three independent patients and in two of their siblings who presented with PCD and situs solitus (i.e., normal position of inner organs). Strikingly, these five patients share one mutant allele (splice defect), which is identical to one of the mutant DNAI1 alleles found in the patient with PCD, reported elsewhere. Finally, this study demonstrates a link between ciliary function and situs determination, since compound mutation heterozygosity in DNAI1 results in PCD with situs solitus or situs inversus (KS).

Axonemal beta heavy chain dynein DNAH9: cDNA sequence, genomic structure, and investigation of its role in primary ciliary dyskinesia

Dyneins are multisubunit protein complexes that couple ATPase activity with conformational changes. They are involved in the cytoplasmatic movement of organelles (cytoplasmic dyneins) and the bending of cilia and flagella (axonemal dyneins). Here we present the first complete cDNA and genomic sequences of a human axonemal dynein beta heavy chain gene, DNAH9, which maps to 17p12. The 14-kb-long cDNA is divided into 69 exons spread over 390 kb. The cDNA sequence of DNAH9 was determined using a combination of methods including 5' rapid amplification of cDNA ends, RT-PCR, and cDNA library screening. RT-PCR using nasal epithelium and testis RNA revealed several alternatively spliced transcripts. The genomic structure was determined using three overlapping BACs sequenced by the Whitehead Institute/MIT Center for Genome Research. The predicted protein, of 4486 amino acids, is highly homologous to sea urchin axonemal beta heavy chain dyneins (67% identity). It consists of an N-terminal stem and a globular C-terminus containing the four P-loops that constitute the motor domain. Lack of proper ciliary and flagellar movement characterizes primary ciliary dyskinesia (PCD), a genetically heterogeneous autosomal recessive disorder with respiratory tract infections, bronchiectasis, male subfertility, and, in 50% of cases, situs inversus (Kartagener syndrome, KS). Dyneins are excellent candidate genes for PCD and KS because in over 50% of cases the ultrastructural defects of cilia are related to the dynein complex. Genotype analysis was performed in 31 PCD families with two or more affected siblings using a highly informative dinucleotide polymorphism located in intron 26 of DNAH9. Two families with concordant inheritance of DNAH9 alleles in affected individuals were observed. A mutation search was performed in these two "candidate families," but only polymorphic variants were found. In the absence of pathogenic mutations, the DNAH9 gene has been excluded as being responsible for autosomal recessive PCD in these families.

Characterization of an axonemal dynein heavy chain expressed early in airway epithelial ciliogenesis

The most conspicuous evidence of airway epithelial maturation and vitality is the presence of motile cilia. In an effort to generate genetic and antigenic markers of airway maturation, injury, and repair, we characterized airway epithelial expression of a gene identified by two human expressed sequence tags that encoded peptides with sequence similarity to an invertebrate ciliary dynein heavy chain (DHC). Molecular analyses showed that the gene has a very large RNA transcript that encodes a very high molecular weight polypeptide with biochemical properties that are characteristic of a dynein heavy chain. Expression of the gene transcript correlated with the presence of ciliated cells in tissues, and immunohistochemical localization of the gene product confirmed its presence in the cilia of mature airway epithelium. In epithelium undergoing ciliogenesis ex vivo, expression of the gene transcript preceded ciliation of the epithelium and the gene product was present in the cytoplasm and at the apical border of nonciliated cells. These data suggested that the gene encodes an axonemal DHC that is expressed early during ciliogenesis, before the appearance of cilia.

Dynein and dynein-related genes

Dyneins are large, multisubunit ATPases that interact with microtubules to generate force. Dyneins move eukaryotic cilia and flagella and are in the cytoplasm, where they are involved in the transport of particles and organelles along microtubules and in the transport of condensed chromosomes during mitosis [reviewed in Holzbaur et al., 1994; Gibbons, 1996]. Defects in human axonemal dynein complexes have been shown to be associated with Kartagener's syndrome, which is characterized by recurrent respiratory tract infections, immotile sperm and situs inversus. Cytoplasmic and axonemal dyneins are composed of heavy, intermediate, and light chains. The best characterised groups of dynein genes so far are those encoding cytoplasmic heavy chains and heavy chains from the outer arms from axonemes. These share extensive sequence similarity and are conserved throughout species. Recently, several genes encoding intermediate and light chains have been identified; these have encoded a remarkable diversity of products, which also seem to be highly conserved between species, although they fall into several complex groups. The structure of dynein heavy chain genes, the emerging knowledge on intermediate and light chain genes and their products, and the possible involvement of dyneins in disease are discussed.

A sequence-ready BAC/PAC contig and partial transcript map of approximately 1.5 Mb in human chromosome 17q25 comprising multiple disease genes

Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant recurrent neuropathy mapped to a 4-cM interval on chromosome 17q25 between the short tandem repeat (STR) markers D17S1603 and D17S802. Chromosome 17q25 in general and the 4-cM HNA region in particular are also implicated in the pathogenesis of a number of tumors (tylosis with esophageal cancer, sporadic breast and ovarian tumors) and harbor a psoriasis susceptibility locus. Initial attempts to construct a yeast artificial chromosome contig failed. Therefore, we have now constructed a complete P1 artificial chromosome (PAC) and bacterial artificial chromosome (BAC) contig of the region flanked by the STR markers D17S1603 and D17S802. The contig contains 22 PAC and 64 BAC clones and covers a physical distance of approximately 1. 5 Mb. A total of 83 sequence-tagged site (STS) markers (10 known STSs and STRs, 56 STSs generated from clone end-fragments, 12 expressed sequence tags, and 5 known genes) were mapped on the contig, resulting in an extremely dense physical map with approximately 1 STS per 20 kb. This sequence-ready PAC and BAC contig will be pivotal for the positional cloning of the HNA gene as well as other disease genes mapping to this region.

Loss-of-function mutations in a human gene related to Chlamydomonas reinhardtii dynein IC78 result in primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a group of heterogeneous disorders of unknown origin, usually inherited as an autosomal recessive trait. Its phenotype is characterized by axonemal abnormalities of respiratory cilia and sperm tails leading to bronchiectasis and sinusitis, which are sometimes associated with situs inversus (Kartagener syndrome) and male sterility. The main ciliary defect in PCD is an absence of dynein arms. We have isolated the first gene involved in PCD, using a candidate-gene approach developed on the basis of documented abnormalities of immotile strains of Chlamydomonas reinhardtii, which carry axonemal ultrastructural defects reminiscent of PCD. Taking advantage of the evolutionary conservation of genes encoding axonemal proteins, we have isolated a human sequence (DNAI1) related to IC78, a C. reinhardtii gene encoding a dynein intermediate chain in which mutations are associated with the absence of outer dynein arms. DNAI1 is highly expressed in trachea and testis and is composed of 20 exons located at 9p13-p21. Two loss-of-function mutations of DNAI1 have been identified in a patient with PCD characterized by immotile respiratory cilia lacking outer dynein arms. In addition, we excluded linkage between this gene and similar PCD phenotypes in five other affected families, providing a clear demonstration of locus heterogeneity. These data reveal the critical role of DNAI1 in the development of human axonemal structures and open up new means for identification of additional genes involved in related developmental defects.

Loss-of-function mutations in a human gene related to Chlamydomonas reinhardtii dynein IC78 result in primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a group of heterogeneous disorders of unknown origin, usually inherited as an autosomal recessive trait. Its phenotype is characterized by axonemal abnormalities of respiratory cilia and sperm tails leading to bronchiectasis and sinusitis, which are sometimes associated with situs inversus (Kartagener syndrome) and male sterility. The main ciliary defect in PCD is an absence of dynein arms. We have isolated the first gene involved in PCD, using a candidate-gene approach developed on the basis of documented abnormalities of immotile strains of Chlamydomonas reinhardtii, which carry axonemal ultrastructural defects reminiscent of PCD. Taking advantage of the evolutionary conservation of genes encoding axonemal proteins, we have isolated a human sequence (DNAI1) related to IC78, a C. reinhardtii gene encoding a dynein intermediate chain in which mutations are associated with the absence of outer dynein arms. DNAI1 is highly expressed in trachea and testis and is composed of 20 exons located at 9p13-p21. Two loss-of-function mutations of DNAI1 have been identified in a patient with PCD characterized by immotile respiratory cilia lacking outer dynein arms. In addition, we excluded linkage between this gene and similar PCD phenotypes in five other affected families, providing a clear demonstration of locus heterogeneity. These data reveal the critical role of DNAI1 in the development of human axonemal structures and open up new means for identification of additional genes involved in related developmental defects.