Turning the Curve Into Straight: Phenogenetics of the Spine Morphology and Coordinate Maintenance in the Zebrafish

C-mannosyltransferase DPY19L1L-mediated Reissner Fiber formation is critical for zebrafish (Danio rerio) body axis straightening

The successful secretion and assembly of subcommissural organ (SCO)-spondin are crucial for Reissner Fiber (RF) formation and body axis straightening in zebrafish. However, the mechanisms underlying RF formation remain largely unknown. Here, we report that the C-mannosyltransferase dpy19l1l (dumpy-19 like 1 like) is expressed in the spinal cord during zebrafish embryonic development. Mutation in dpy19l1l resulted in idiopathic scoliosis (IS)-like body axis curvature in the absence of muscle or cilia defects. URP2 expression was down-regulated in dpy19l1l-/- mutants. Notably, RF formation was impaired in dpy19l1l-/- mutants, and a similar phenotype was induced in wild-type embryos by injecting messenger RNA encoding a C-mannosylation catalytic site-mutated dpy19l1l variant (E106A mdpy19l1l). Furthermore, E106A mDPY19L1L failed to glycosylate Flag-tagged SCO-spondin TSRs (thrombospondin type 1 repeats). Our findings suggest that DPY19L1L-mediated C-mannosylation of SCO-spondin TSRs promotes RF formation and URP2 induction, representing a critical supplementary mechanism for body axis straightening in zebrafish.

Advances in genetic factors of adolescent idiopathic scoliosis: a bibliometric analysis

Objective

This study offers a bibliometric analysis of the current situation, hotspots, and cutting-edge domains of genetic factors of adolescent idiopathic scoliosis (AIS).

Methods

All publications related to genetic factors of AIS from January 1, 1992, to February 28, 2023, were searched from the Web of Science. CiteSpace software was employed for bibliometric analysis, collecting information about countries, institutions, authors, journals, and keywords of each article.

Results

A cumulative number of 308 articles have been ascertained. Since 2006, publications relating to genetic factors of AIS have significantly increased. China leads in both productivity and influence in this area, with the Chinese Academy of Medical Sciences being the most productive institution. The most prolific scholars in this field are Y. Qiu and Z. Z. Zhu. The publications that contributed the most were from Spine and European Spine Journal. The most prominent keywords in the genetic factors of AIS were "fibrillin gene", "menarche", "calmodulin", "estrogen receptor gene", "linkage analysis", "disc degeneration", "bone mineral density", "melatonin signaling dysfunction", "collagen gene", "mesenchymal stem cell", "LBX1", "promoter polymorphism", "Bone formation", "cerebrospinal fluid flow" and "extracellular matrix".

Conclusion

This analysis provides the frontiers and trends of genetic factors in AIS, including relevant research, partners, institutions and countries.

Identification of a novel splice site mutation in the DNAAF4 gene of a Chinese patient with primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a rare hereditary orphan condition that results in variable phenotypes, including infertility. About 50 gene variants are reported in the scientific literature to cause PCD, and among them, dynein axonemal assembly factor 4 ( DNAAF4 ) has been recently reported. DNAAF4 has been implicated in the preassembly of a multiunit dynein protein essential for the normal function of locomotory cilia as well as flagella. In the current study, a single patient belonging to a Chinese family was recruited, having been diagnosed with PCD and asthenoteratozoospermia. The affected individual was a 32-year-old male from a nonconsanguineous family. He also had abnormal spine structure and spinal cord bends at angles diagnosed with scoliosis. Medical reports, laboratory results, and imaging data were investigated. Whole-exome sequencing, Sanger sequencing, immunofluorescence analysis, hematoxylin-eosin staining, and in silico functional analysis, including protein modeling and docking studies, were used. The results identified DNAAF4 disease-related variants and confirmed their pathogenicity. Genetic analysis through whole-exome sequencing identified two pathogenic biallelic variants in the affected individual. The identified variants were a hemizygous splice site c.784-1G>A and heterozygous 20.1 Kb deletion at the DNAAF4 locus, resulting in a truncated and functionless DNAAF4 protein. Immunofluorescence analysis indicated that the inner dynein arm was not present in the sperm flagellum, and sperm morphological analysis revealed small sperm with twisted and curved flagella or lacking flagella. The current study found novel biallelic variants causing PCD and asthenoteratozoospermia, extending the range of DNAAF4 pathogenic variants in PCD and associated with the etiology of asthenoteratozoospermia. These findings will improve our understanding of the etiology of PCD.

Case Report: DNAAF4 Variants Cause Primary Ciliary Dyskinesia and Infertility in Two Han Chinese Families

Background: Primary ciliary dyskinesia (PCD) is a rare genetic disorder, predominantly autosomal recessive. The dynein axonemal assembly factor 4 (DNAAF4) is mainly involved in the preassembly of multisubunit dynein protein, which is fundamental to the proper functioning of cilia and flagella. There are few reports of PCD-related pathogenic variants of DNAAF4, and almost no DNAAF4-related articles focused on sperm phenotype. Moreover, the association between DNAAF4 and scoliosis has never been reported, to the best of our knowledge.

Materials and Methods: We recruited two patients with a clinical diagnosis of PCD. One came from a consanguineous and another from a non-consanguineous family. Clinical data, laboratory test results, and imaging data were analyzed. Through whole exome sequencing, immunofluorescence, electron microscopy, high-speed video microscopy analysis, and hematoxylin–eosin (HE) staining, we identified the disease-associated variants and validated the pathogenicity.

Results: Proband 1 (P1, F1: II-1), a 19-year-old man, comes from a non-consanguineous family-I, and proband 2 (P2, F2: II-1), a 37-year-old woman, comes from a consanguineous family-II. Both had sinusitis, bronchiectasis, situs inversus, and scoliosis. P1 also had asthenoteratozoospermia, and P2 had an immature uterus. Two homozygous pathogenic variants in DNAAF4 (NM_130810.4), c.988C > T, p.(Arg330Trp), and DNAAF4 (NM_130810.4), c.733 C > T, p.(Arg245*), were identified through whole exome sequencing. High-speed microscopy analysis showed that most of the cilia were static in P1, with complete static of the respiratory cilia in P2. Immunofluorescence showed that the outer dynein arms (ODA) and inner dynein arms (IDA) were absent in the respiratory cilia of both probands, as well as in the sperm flagellum of P1. Transmission electron microscopy revealed the absence of ODA and IDA of respiratory cilia of P2, and HE staining showed irregular, short, absent, coiled, and bent flagella.

Conclusion: Our study identified a novel variant c.733C > T, which expanded the spectrum of DNAAF4 variants. Furthermore, we linked DNAAF4 to asthenoteratozoospermia and likely scoliosis in patients with PCD. This study will contribute to a better understanding of PCD.