Appendage-resident epithelial cells expedite wound healing response in adult zebrafish.

Adult zebrafish are able to heal large-sized cutaneous wounds in hours with little to no scarring. This rapid re-epithelialization is crucial for preventing infection and jumpstarting the subsequent regeneration of damaged tissues. Despite significant progress in understanding this process, it remains unclear how vast numbers of epithelial cells are orchestrated on an organismic scale to ensure the timely closure of millimeter-sized wounds. Here, we report an unexpected role of adult zebrafish appendages (fins) in accelerating the re-epithelialization process. Through whole-body monitoring of single-cell dynamics in live animals, we found that fin-resident epithelial cells (FECs) are highly mobile and migrate to cover wounds in nearby body regions. Upon injury, FECs readily undergo organ-level mobilization, allowing for coverage of body surfaces of up to 4.78 mm2 in less than 8 h. Intriguingly, long-term fate-tracking experiments revealed that the migratory FECs are not short-lived at the wound site; instead, the cells can persist on the body surface for more than a year. Our experiments on "fin-less" and "fin-gaining" individuals demonstrated that the fin structures are not only capable of promoting rapid re-epithelialization but are also necessary for the process. We further found that fin-enriched extracellular matrix laminins promote the active migration of FECs by facilitating lamellipodia formation. These findings lead us to conclude that appendage structures in regenerative vertebrates, such as fins, may possess a previously unrecognized function beyond serving as locomotor organs. The appendages may also act as a massive reservoir of healing cells, which speed up wound closure and tissue repair.

Mechano-chemical enforcement of tendon apical ECM into nano-filaments during Drosophila flight muscle development.

Contractile tension is critical for musculoskeletal system development and maintenance. In insects, the muscular force is transmitted to the exoskeleton through the tendon cells and tendon apical extracellular matrix (ECM). In Drosophila, we found tendon cells secrete Dumpy (Dpy), a zona pellucida domain (ZPD) protein, to form the force-resistant filaments in the exuvial space, anchoring the tendon cells to the pupal cuticle. We showed that Dpy undergoes filamentous conversion in response to the tension increment during indirect flight muscle development. We also found another ZPD protein Quasimodo (Qsm) protects the notum epidermis from collapsing under the muscle tension by enhancing the tensile strength of Dpy filaments. Qsm is co-transported with Dpy in the intracellular vesicles and diffuses into the exuvial space after secretion. Tissue-specific qsm expression rescued the qsm mutant phenotypes in distant tissues, suggesting Qsm can function in a long-range, non-cell-autonomous manner. In the cell culture assay, Qsm interacts with Dpy-ZPD and promotes secretion and polymerization of Dpy-ZPD. The roles of Qsm underlies the positive feedback mechanism of force-dependent organization of Dpy filaments, providing new insights into apical ECM remodeling through the unconventional interaction of ZPD proteins.

Glial expression of disease-associated poly-glutamine proteins impairs the blood-brain barrier in Drosophila.

Expansion of poly-glutamine (polyQ) stretches in several proteins has been linked to neurodegenerative diseases. The effects of polyQ-expanded proteins on neurons have been extensively studied, but their effects on glia remain unclear. We found that expression of distinct polyQ proteins exclusively in all glia or specifically in the blood-brain barrier (BBB) and blood-retina barrier (BRB) glia caused cell-autonomous impairment of BBB/BRB integrity, suggesting that BBB/BRB glia are most vulnerable to polyQ-expanded proteins. Furthermore, we also found that BBB/BRB leakage in Drosophila is reflected in reversed waveform polarity on the basis of electroretinography (ERG), making ERG a sensitive method to detect BBB/BRB leakage. The polyQ-expanded protein Atxn3-84Q forms aggregates, induces BBB/BRB leakage, restricts Drosophila lifespan and reduces the level of Repo (a pan-glial transcriptional factor required for glial differentiation). Expression of Repo in BBB/BRB glia can rescue BBB/BRB leakage, suggesting that the reduced expression of Repo is important for the effect of polyQ on BBB/BRB impairment. Coexpression of the chaperon HSP40 and HSP70 effectively rescues the effects of Atxn3-84Q, indicating that polyQ protein aggregation in glia is deleterious. Intriguingly, coexpression of wild-type Atxn3-27Q can also rescue BBB/BRB impairment, suggesting that normal polyQ protein may have a protective function.

FGF /FGFR signal induces trachea extension in the drosophila visual system.

The Drosophila compound eye is a large sensory organ that places a high demand on oxygen supplied by the tracheal system. Although the development and function of the Drosophila visual system has been extensively studied, the development and contribution of its tracheal system has not been systematically examined. To address this issue, we studied the tracheal patterns and developmental process in the Drosophila visual system. We found that the retinal tracheae are derived from air sacs in the head, and the ingrowth of retinal trachea begin at mid-pupal stage. The tracheal development has three stages. First, the air sacs form near the optic lobe in 42-47% of pupal development (pd). Second, in 47-52% pd, air sacs extend branches along the base of the retina following a posterior-to-anterior direction and further form the tracheal network under the fenestrated membrane (TNUFM). Third, the TNUFM extend fine branches into the retina following a proximal-to-distal direction after 60% pd. Furthermore, we found that the trachea extension in both retina and TNUFM are dependent on the FGF(Bnl)/FGFR(Btl) signaling. Our results also provided strong evidence that the photoreceptors are the source of the Bnl ligand to guide the trachea ingrowth. Our work is the first systematic study of the tracheal development in the visual system, and also the first study demonstrating the interactions of two well-studied systems: the eye and trachea.

Optimal Te-doping in GaSe for non-linear applications.

Centimeter-sized Te-doped GaSe ingots were grown from the charge compositions of GaSe with nominals 0.05, 0.1, 0.5, 1, and 3 mass% Te, which were identified as ε-GaSe:Te (0.01, 0.07, 0.38, 0.67, and 2.07 mass%) single crystals. The evolution of the absorption peaks of the phonon modes E'(2) (≈ 0.584 THz) and E"(2) (1.77 THz) on Te-doping in GaSe:Te crystals was studied by THz time-domain spectroscopy. This study proposes that the evolution of both E'(2) and E''(2) absorption peaks correlates well with the optical quality of Te-doped GaSe crystals, which was confirmed by experimental results on the efficiency of THz generation by optical rectification. Maximal intensity of the absorption peak of the rigid layer mode E'(2) is proposed as a criterion for identification of optimal Te-doping in GaSe crystals.

Widely linear and non-phase-matched optical-to-terahertz conversion on GaSe:Te crystals.

We demonstrate the widely linear and broadband terahertz (THz) generation on GaSe:Te crystals by femtosecond laser pulses. It was found that the dopant, Te atoms, in GaSe crystals significantly enhances the efficiency of THz generation, and its central frequency can be tuned by varying the crystal thickness through non-phase-matched optical rectification. Moreover, the wide-ranging linearity for the optical-to-THz conversion and central-frequency-tunable THz generation promise for GaSe:Te crystals to be potential materials for high-power (>1.36 µW) THz applications.

Family of V(III)-tristhiolato complexes relevant to functional models of vanadium nitrogenase: synthesis and electronic structure investigations by means of high-frequency and -field electron paramagnetic resonance coupled to quantum chemical computations.

A series of V(III) complexes of varying coordination number (5, 6, and 7) all containing the PS3 ligand (PS3 = trianion of tris(2-thiophenyl)phosphine and its derivatives with other phenyl substituents) has been prepared and structurally characterized. The complexes have general formula [V(PS3)L(n)](0,-), where n = 1 (from L = Cl(-), 1-Me-Im, N(3)(-)), 2 (from L = 2,2'-bpy; counting each N of the bidentate ligand), and 3 (from L = 1-Me-Im, N(2)H(4)). The complexes have also been investigated by direct current (DC) magnetic susceptibility and high-frequency and -field electron paramagnetic resonance (HFEPR). HFEPR, supported by magnetometry, has provided accurate spin Hamiltonian parameters that describe the S = 1 spin ground state of the complexes. Of particular interest are the zero-field splitting (zfs) parameters which, together with structural data, are the empirical starting point for detailed computational studies. The computational methods included density functional theory (DFT), which was only marginally successful, and more advanced ab initio methods (CASSCF and SORCI). The zfs in these complexes is relatively small in magnitude (|D| approximately 1 cm(-1)) and is the result of multiple, often counteracting, spin-orbit coupling (SOC) and spin-spin coupling (SSC) contributions. The specific origin of each of these contributions is described in detail. The results indicate the level of electronic structure calculation possible for transition metal complexes even with multiple unpaired electrons and highly covalent, heavier atom donor ligands.

DAZAP1, an hnRNP protein, is required for normal growth and spermatogenesis in mice.

DAZAP1 (Deleted in Azoospermia Associated Protein 1) is a ubiquitous hnRNP protein that is expressed most abundantly in the testis. Its ability to shuttle between the nucleus and the cytoplasm and its exclusion from the transcriptionally inactive XY body in pachytene spermatocytes implicate it in mRNA transcription and transport. We generated Dazap1 mutant alleles to study the role of DAZAP1 in mouse development. Most mice homozygous for the null allele as well as a hypomorphic Fn allele died soon after birth. The few Dazap1(Fn/Fn) mice that survived could nonetheless live for more than a year. They appeared and behaved normally but were much smaller in size compared to their wild-type and heterozygous littermates. Both male and female Dazap1(Fn/Fn) mice were sterile. Males had small testes, and the seminiferous tubules were atrophic with increased numbers of apoptotic cells. The tubules contained many germ cells, including pachytene spermatocytes with visible XY-bodies and diplotene spermatocytes, but no post-meiotic cells. FACS analyses confirmed the absence of haploid germ cells, indicating spermatogenesis arrested right before the meiotic division. Female Dazap1(Fn/Fn) mice had small ovaries that contained normal-appearing follicles, yet their pregnancy produced no progeny due to failure in embryonic development. The phenotypes of Dazap1 mutant mice indicate that DAZAP1 is not only essential for spermatogenesis, but also required for the normal growth and development of mice.