Gallium Oxide for Gas Sensor Applications: A Comprehensive Review.

Ga2O3 has emerged as a promising ultrawide bandgap semiconductor for numerous device applications owing to its excellent material properties. In this paper, we present a comprehensive review on major advances achieved over the past thirty years in the field of Ga2O3-based gas sensors. We begin with a brief introduction of the polymorphs and basic electric properties of Ga2O3. Next, we provide an overview of the typical preparation methods for the fabrication of Ga2O3-sensing material developed so far. Then, we will concentrate our discussion on the state-of-the-art Ga2O3-based gas sensor devices and put an emphasis on seven sophisticated strategies to improve their gas-sensing performance in terms of material engineering and device optimization. Finally, we give some concluding remarks and put forward some suggestions, including (i) construction of hybrid structures with two-dimensional materials and organic polymers, (ii) combination with density functional theoretical calculations and machine learning, and (iii) development of optical sensors using the characteristic optical spectra for the future development of novel Ga2O3-based gas sensors.

Molecular Mechanisms of Alveolar Epithelial Stem Cell Senescence and Senescence-Associated Differentiation Disorders in Pulmonary Fibrosis.

Pulmonary senescence is accelerated by unresolved DNA damage response, underpinning susceptibility to pulmonary fibrosis. Recently it was reported that the SARS-Cov-2 viral infection induces acute pulmonary epithelial senescence followed by fibrosis, although the mechanism remains unclear. Here, we examine roles of alveolar epithelial stem cell senescence and senescence-associated differentiation disorders in pulmonary fibrosis, exploring the mechanisms mediating and preventing pulmonary fibrogenic crisis. Notably, the TGF-ß signalling pathway mediates alveolar epithelial stem cell senescence by mechanisms involving suppression of the telomerase reverse transcriptase gene in pulmonary fibrosis. Alternatively, telomere uncapping caused by stress-induced telomeric shelterin protein TPP1 degradation mediates DNA damage response, pulmonary senescence and fibrosis. However, targeted intervention of cellular senescence disrupts pulmonary remodelling and fibrosis by clearing senescent cells using senolytics or preventing senescence using telomere dysfunction inhibitor (TELODIN). Studies indicate that the development of senescence-associated differentiation disorders is reprogrammable and reversible by inhibiting stem cell replicative senescence in pulmonary fibrosis, providing a framework for targeted intervention of the molecular mechanisms of alveolar stem cell senescence and pulmonary fibrosis. Abbreviations: DPS, developmental programmed senescence; IPF, idiopathic pulmonary fibrosis; OIS, oncogene-induced replicative senescence; SADD, senescence-associated differentiation disorder; SALI, senescence-associated low-grade inflammation; SIPS, stress-induced premature senescence; TERC, telomerase RNA component; TERT, telomerase reverse transcriptase; TIFs, telomere dysfunction-induced foci; TIS, therapy-induced senescence; VIS, virus-induced senescence.

Telomere Dysfunction in Idiopathic Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis is an age-dependent progressive and fatal lung disease of unknown etiology, which is characterized by the excessive accumulation of extracellular matrix inside the interstitial layer of the lung parenchyma that leads to abnormal scar architecture and compromised lung function capacity. Recent genetic studies have attributed the pathological genes or genetic mutations associated with familial idiopathic pulmonary fibrosis (IPF) and sporadic IPF to telomere-related components, suggesting that telomere dysfunction is an important determinant of this disease. In this study, we summarized recent advances in our understanding of how telomere dysfunction drives IPF genesis. We highlighted the key role of alveolar stem cell dysfunction caused by telomere shortening or telomere uncapping, which bridged the gap between telomere abnormalities and fibrotic lung pathology. We emphasized that senescence-associated secretory phenotypes, innate immune cell infiltration, and/or inflammation downstream of lung stem cell dysfunction influenced the native microenvironment and local cell signals, including increased transforming growth factor-beta (TGF-ß) signaling in the lung, to induce pro-fibrotic conditions. In addition, the failed regeneration of new alveoli due to alveolar stem cell dysfunction might expose lung cells to elevated mechanical tension, which could activate the TGF-ß signaling loop to promote the fibrotic process, especially in a periphery-to-center pattern as seen in IPF patients. Understanding the telomere-related molecular and pathophysiological mechanisms of IPF would provide new insights into IPF etiology and therapeutic strategies for this fatal disease.

Pulmonary Alveolar Stem Cell Senescence, Apoptosis, and Differentiation by p53-Dependent and -Independent Mechanisms in Telomerase-Deficient Mice.

Pulmonary premature ageing and fibrogenesis as in idiopathic pulmonary fibrosis (IPF) occur with the DNA damage response in lungs deficient of telomerase. The molecular mechanism mediating pulmonary alveolar cell fates remains to be investigated. The present study shows that naturally occurring ageing is associated with the DNA damage response (DDR) and activation of the p53 signalling pathway. Telomerase deficiency induced by telomerase RNA component (TERC) knockout (KO) accelerates not only replicative senescence but also altered differentiation and apoptosis of the pulmonary alveolar stem cells (AEC2) in association with increased innate immune natural killer (NK) cells in TERC KO mice. TERC KO results in increased senescence-associated heterochromatin foci (SAHF) marker HP1γ, p21, p16, and apoptosis-associated cleaved caspase-3 in AEC2. However, additional deficiency of the tumour suppressor p53 in the Trp53-/- allele of the late generation of TERC KO mice attenuates the increased senescent and apoptotic markers significantly. Moreover, p53 deficiency has no significant effect on the increased gene expression of T1α (a marker of terminal differentiated AEC1) in AEC2 of the late generation of TERC KO mice. These findings demonstrate that, in natural ageing or premature ageing accelerated by telomere shortening, pulmonary senescence and IPF develop with alveolar stem cell p53-dependent premature replicative senescence, apoptosis, and p53-independent differentiation, resulting in pulmonary senescence-associated low-grade inflammation (SALI). Our studies indicate a natural ageing-associated molecular mechanism of telomerase deficiency-induced telomere DDR and SALI in pulmonary ageing and IPF.

Pulmonary alveolar stem cells undergo senescence, apoptosis and differentiation by p53-dependent and -independent mechanisms in telomerase deficient mice.

Pulmonary senescence and fibrosis occur with deoxyribonucleic acid (DNA) damage response in the lungs deficient of telomerase. The molecular mechanism mediating pulmonary alveolar cell fates remains to be investigated. The present study shows that pulmonary alveolar epithelial type 2 cells (AEC2) (alveolar stem cells) undergo not only replicative senescence, but also apoptosis and differentiation in association with increased innate immune natural killer (NK) cells in telomerase knockout (KO) mice. Telomerase ribonucleic acid (RNA) component (TERC) deficiency results in increased senescence-associated heterochromatin foci marker HP1γ, p21, p16 and apoptosis-associated cleaved caspase-3 in AEC2. However, p53 deficiency in the Trp53-/- allele of the late generation of TERC KO mice attenuates the increased senescent and apoptotic markers significantly. Moreover, p53 deficiency has no significant effect on the increased gene expression of T1α (a marker of terminal differentiated alveolar epithelial type 1 cells [AEC1]) in AEC2 of the late generation of TERC KO mice. Collectively, our findings suggest that pulmonary senescence takes place in deficiency of telomerase RNA component with the alveolar stem cells undergoing p53-dependent senescence and apoptosis as well as p53-independent differentiation.

Telomere shortening activates TGF-ß/Smads signaling in lungs and enhances both lipopolysaccharide and bleomycin-induced pulmonary fibrosis.

Telomere shortening is associated with idiopathic pulmonary fibrosis (IPF), a high-morbidity and high-mortality lung disease of unknown etiology. However, the underlying mechanisms remain largely unclear. In this study, wild-type (WT) mice with normal telomeres and generation 3 (G3) or G2 telomerase RNA component (TERC) knockout Terc-/- mice with short telomeres were treated with and without lipopolysaccharide (LPS) or bleomycin by intratracheal injection. We show that under LPS induction, G3 Terc-/- mice develop aggravated pulmonary fibrosis as indicated by significantly increased α-SMA, collagen I and hydroxyproline content. Interestingly, TGF-ß/Smads signaling is markedly activated in the lungs of G3 Terc-/- mice, as indicated by markedly elevated levels of phosphorylated Smad3 and TGF-ß1, compared with those of WT mice. This TGF-ß/Smads signaling activation is significantly increased in the lungs of LPS-treated G3 Terc-/- mice compared with those of LPS-treated WT or untreated G3 Terc-/- mice. A similar pattern of TGF-ß/Smads signaling activation and the enhancing role of telomere shortening in pulmonary fibrosis are also confirmed in bleomycin-induced model. Moreover, LPS challenge produced more present cellular senescence, apoptosis and infiltration of innate immune cells, including macrophages and neutrophils in the lungs of G3 Terc-/- mice, compared with WT mice. To our knowledge, this is the first time to report telomere shortening activated TGF-ß/Smads signaling in lungs. Our data suggest that telomere shortening cooperated with environment-induced lung injury accelerates the development of pulmonary fibrosis, and telomere shortening confers an inherent enhancing factor to the genesis of IPF through activation of TGF-ß/Smads signaling.

P-Channel InGaN/GaN heterostructure metal-oxide-semiconductor field effect transistor based on polarization-induced two-dimensional hole gas.

The concept of p-channel InGaN/GaN heterostructure field effect transistor (FET) using a two-dimensional hole gas (2DHG) induced by polarization effect is demonstrated. The existence of 2DHG near the lower interface of InGaN/GaN heterostructure is verified by theoretical simulation and capacitance-voltage profiling. The metal-oxide-semiconductor FET (MOSFET) with Al2O3 gate dielectric shows a drain-source current density of 0.51 mA/mm at the gate voltage of -2 V and drain bias of -15 V, an ON/OFF ratio of two orders of magnitude and effective hole mobility of 10 cm(2)/Vs at room temperature. The normal operation of MOSFET without freeze-out at 8 K further proves that the p-channel behavior is originated from the polarization-induced 2DHG.

Telomerase Deficiency Causes Alveolar Stem Cell Senescence-associated Low-grade Inflammation in Lungs.

Mutations of human telomerase RNA component (TERC) and telomerase reverse transcriptase (TERT) are associated with a subset of lung aging diseases, but the mechanisms by which TERC and TERT participate in lung diseases remain unclear. In this report, we show that knock-out (KO) of the mouse gene Terc or Tert causes pulmonary alveolar stem cell replicative senescence, epithelial impairment, formation of alveolar sacs, and characteristic inflammatory phenotype. Deficiency in TERC or TERT causes a remarkable elevation in various proinflammatory cytokines, including IL-1, IL-6, CXCL15 (human IL-8 homolog), IL-10, TNF-α, and monocyte chemotactic protein 1 (chemokine ligand 2 (CCL2)); decrease in TGF-ß1 and TGFßRI receptor in the lungs; and spillover of IL-6 and CXCL15 into the bronchoalveolar lavage fluids. In addition to increased gene expressions of α-smooth muscle actin and collagen 1α1, suggesting myofibroblast differentiation, TERC deficiency also leads to marked cellular infiltrations of a mononuclear cell population positive for the leukocyte common antigen CD45, low-affinity Fc receptor CD16/CD32, and pattern recognition receptor CD11b in the lungs. Our data demonstrate for the first time that telomerase deficiency triggers alveolar stem cell replicative senescence-associated low-grade inflammation, thereby driving pulmonary premature aging, alveolar sac formation, and fibrotic lesion.

Cellular senescence occurred widespread to multiple selective sites in the fetal tissues and organs of mice.

Cellular senescence protects multicellular organisms from tissue overgrowth including cancer, and contributes to tissue ageing. With stable cell cycle arrests, cellular senescence has been mostly studied in the adult tissues of mammals. In the present study, we report widespread cellular senescence within certain time windows of late-phase normal development of mouse embryos. Using in situ senescence-associated ß-galactosidase (SA-ß-gal) staining, we showed SA-ß-gal activity in selected cell populations of the brain, stomach, interdigital webs, tail, ear, limbs and nasal mouth area on gestation day 14.5 of the mouse embryos. On day 18.5 of gestation, selected cells in the intestines and bone developmental areas showed SA-ß-gal activity. The chondrocytes in ossification zones were significantly marked by the activities of SA-ß-gal, p21, p15 and Hp1Y, suggesting activation of the cell cycle checkpoint by the p53 and Rb pathways, and development of senescence-associated heterochromatic foci. Throughout gestation days 14.5-18.5, the trophoblast cells in the labyrinth layer of the placentas also showed strong activities of SA-ß-gal, p53 and p21. Increased expressions of p19, p16 and Rb of the p16/Rb pathway, and reduced expressions of Ki67 were also observed in the placentas. Taken together, the present findings suggest that cellular senescence represents an essential mechanism at multiple sites including the fetal bone forming zones and placenta during mammalian embryonic development, playing potential roles in the full embryonic development of tissue growth and organ formation.

Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n+-GaN polarization-induced backward tunneling junction grown by metal-organic chemical vapor deposition on sapphire substrate.

Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n(+)-GaN polarization-induced backward tunneling junction (PIBTJ) was grown by metal-organic chemical vapor deposition on sapphire substrate. A self-consistent solution of Poisson-Schrödinger equations combined with polarization-induced theory was used to model PIBTJ structure, energy band diagrams and free carrier concentrations distribution. The PIBTJ displays reliable and reproducible backward tunneling with a current density of 3 A/cm(2) at the reverse bias of -1 V. The absence of negative differential resistance behavior of PIBTJ at forward bias can mainly be attributed to the hole compensation centers, including C, H and O impurities, accumulated at the p-GaN/Mg-doped AlGaN heterointerface.

Impact of tumor vascularity on responsiveness to antiangiogenesis in a prostate cancer stem cell-derived tumor model.

Drugs that target the tumor vasculature and inhibit angiogenesis are widely used for cancer treatment. Individual tumors show large differences in vascularity, but it is uncertain how these differences affect responsiveness to antiangiogenesis. We investigated this question using two closely related prostate cancer models that differ markedly in tumor vascularity: PC3, which has very low vascularity, and the PC3-derived cancer stem-like cell holoclone PC3/2G7, which forms tumors with high microvessel density, high tumor blood flow, and low hypoxia compared with parental PC3 tumors. Three angiogenesis inhibitors (axitinib, sorafenib, and DC101) all induced significantly greater decreases in tumor blood flow and microvessel density in PC3/2G7 tumors compared with PC3 tumors, as well as significantly greater decreases in tumor cell proliferation and cell viability and a greater increase in apoptosis. The increased sensitivity of PC3/2G7 tumors to antiangiogenesis indicates they are less tolerant of low vascularity and suggests they become addicted to their oxygen- and nutrient-rich environment. PC3/2G7 tumors showed strong upregulation of the proangiogenic factors chemokine ligand 2 (CCL2) and VEGFA compared with PC3 tumors, which may contribute to their increased vascularity, and they have significantly lower endothelial cell pericyte coverage, which may contribute to their greater sensitivity to antiangiogenesis. Interestingly, high levels of VEGF receptor-2 were expressed on PC3 but not PC3/2G7 tumor cells, which may contribute to the growth static response of PC3 tumors to VEGF-targeted antiangiogenesis. Finally, prolonged antiangiogenic treatment led to resumption of PC3/2G7 tumor growth and neovascularization, indicating these cancer stem-like cell-derived tumors can adapt and escape from antiangiogenesis.

Wavelength-dependent backscattering measurements for quantitative monitoring of apoptosis, part 1: early and late spectral changes are indicative of the presence of apoptosis in cell cultures.

Apoptosis, a form of programmed cell death with unique morphological and biochemical features, is dysregulated in cancer and is activated by many cancer chemotherapeutic drugs. Noninvasive assays for apoptosis in cell cultures can aid in screening of new anticancer agents. We have previously demonstrated that elastic scattering spectroscopy can monitor apoptosis in cell cultures. In this report we present data on monitoring the detailed time-course of scattering changes in a Chinese hamster ovary (CHO) and PC-3 prostate cancer cells treated with staurosporine to induce apoptosis. Changes in the backscattering spectrum are detectable within 10 min, and continue to progress up to 48 h after staurosporine treatment, with the magnitude and kinetics of scattering changes dependent on inducer concentration. Similar responses were observed in CHO cells treated with several other apoptosis-inducing protocols. Early and late scattering changes were observed under conditions shown to induce apoptosis via caspase activity assay and were absent under conditions where apoptosis was not induced. Finally, blocking caspase activity and downstream apoptotic morphology changes prevented late scattering changes. These observations demonstrate that early and late changes in wavelength-dependent backscattering correlate with the presence of apoptosis in cell cultures and that the late changes are specific to apoptosis.

Wavelength-dependent backscattering measurements for quantitative monitoring of apoptosis, part 2: early spectral changes during apoptosis are linked to apoptotic volume decrease.

Elastic scattering spectroscopy (ESS), in the form of wavelength-dependent backscattering measurements, can be used to monitor apoptosis in cell cultures. Early changes in backscattering upon apoptosis induction are characterized by an overall decrease in spectral slope and begin as early as 10 to 15 min post-treatment, progressing over the next 6 to 8 h. The timescale of early scattering changes is consistent with reports of the onset of apoptotic volume decrease (AVD). Modeling cellular scattering with a fixed distribution of sizes and a decreasing index ratio, as well as an increased contribution of the whole cell to cellular scattering, resulting from increased cytoplasmic density, is also consistent with observed spectral changes. Changes in ESS signal from cells undergoing osmotically-induced volume decrease in the absence of apoptosis were similar, but smaller in magnitude, to those of apoptotic cells. Further, blockage of Cl(-) channels, which blocks AVD and delays apoptosis, blocked the early scattering changes, indicating that the early scattering changes during apoptosis result, at least partially, from AVD. Work continues to identify the additional sources of early spectral scattering changes that result from apoptosis induction.

PC3 prostate tumor-initiating cells with molecular profile FAM65Bhigh/MFI2low/LEF1low increase tumor angiogenesis.

BACKGROUND: Cancer stem-like cells are proposed to sustain solid tumors by virtue of their capacity for self-renewal and differentiation to cells that comprise the bulk of the tumor, and have been identified for a variety of cancers based on characteristic clonal morphologies and patterns of marker gene expression. METHODS: Single cell cloning and spheroid culture studies were used to identify a population of cancer stem-like cells in the androgen-independent human prostate cancer cell line PC3. RESULTS: We demonstrate that, under standard culture conditions, ~10% of PC3 cells form holoclones with cancer stem cell characteristics. These holoclones display high self-renewal capability in spheroid formation assays under low attachment and serum-free culture conditions, retain their holoclone morphology when passaged at high cell density, exhibit moderate drug resistance, and show high tumorigenicity in scid immunodeficient mice. PC3 holoclones readily form spheres, and PC3-derived spheres yield a high percentage of holoclones, further supporting their cancer stem cell-like nature. We identified one gene, FAM65B, whose expression is consistently up regulated in PC3 holoclones compared to paraclones, the major cell morphology in the parental PC3 cell population, and two genes, MFI2 and LEF1, that are consistently down regulated. This molecular profile, FAM65Bhigh/MFI2low/LEF1low, also characterizes spheres generated from parental PC3 cells. The PC3 holoclones did not show significant enriched expression of the putative prostate cancer stem cell markers CD44 and integrin α2ß1. PC3 tumors seeded with holoclones showed dramatic down regulation of FAM65B and dramatic up regulation of MFI2 and LEF1, and unexpectedly, a marked increase in tumor vascularity compared to parental PC3 tumors, suggesting a role of cancer stem cells in tumor angiogenesis. CONCLUSIONS: These findings support the proposal that PC3 tumors are sustained by a small number of tumor-initiating cells with stem-like characteristics, including strong self-renewal and pro-angiogenic capability and marked by the expression pattern FAM65Bhigh/MFI2low/LEF1low. These markers may serve as targets for therapies designed to eliminate cancer stem cell populations associated with aggressive, androgen-independent prostate tumors such as PC3.

Pleiotrophin regulates lung epithelial cell proliferation and differentiation during fetal lung development via beta-catenin and Dlk1.

The role of pleiotrophin in fetal lung development was investigated. We found that pleiotrophin and its receptor, protein-tyrosine phosphatase receptor beta/zeta, were highly expressed in mesenchymal and epithelial cells of the fetal lungs, respectively. Using isolated fetal alveolar epithelial type II cells, we demonstrated that pleiotrophin promoted fetal type II cell proliferation and arrested type II cell trans-differentiation into alveolar epithelial type I cells. Pleiotrophin also increased wound healing of injured type II cell monolayer. Knockdown of pleiotrophin influenced lung branching morphogenesis in a fetal lung organ culture model. Pleiotrophin increased the tyrosine phosphorylation of beta-catenin, promoted beta-catenin translocation into the nucleus, and activated T cell factor/lymphoid enhancer factor transcription factors. Dlk1, a membrane ligand that initiates the Notch signaling pathway, was identified as a downstream target of the pleiotrophin/beta-catenin pathway by endogenous dlk1 expression, promoter assay, and chromatin immunoprecipitation. These results provide evidence that pleiotrophin regulates fetal type II cell proliferation and differentiation via integration of multiple signaling pathways including pleiotrophin, beta-catenin, and Notch pathways.

Lin28 modulates cell growth and associates with a subset of cell cycle regulator mRNAs in mouse embryonic stem cells.

Lin28 is highly expressed in human and mouse embryonic stem (ES) cells. Here, we show that in mouse ES cells, specific repression of Lin28 results in decreased cell proliferation, while overexpression of Lin28 accelerates cell proliferation. Further, Lin28 associates specifically with ribonucleoprotein particles containing mRNAs for cyclins A and B and cdk4. Importantly, changes in Lin28 levels lead to corresponding changes in the levels of these proteins, and sequences from the 3' untranslated regions of cyclin B and cdk4 mRNAs exhibit stimulatory effects on translation of reporter genes in a Lin28-dependent fashion. Thus, we postulate that Lin28 may play a role in the regulation of translation of genes important for the growth and maintenance of pluripotent cells.

Receptor-mediated delivery of siRNAs by tethered nucleic acid base-paired interactions.

We report a new strategy for cell-type-specific delivery of functional siRNAs into cells. The method involves the noncovalent attachment of siRNAs to ligand-conjugated oligodeoxynucleotides via nucleic acid base-paired interactions. The resulting complexes can be directly applied to cells, leading to specific cellular uptake and gene silencing. The method is simple, economical, and can be easily adapted for other cell surface receptors. Here we show the application of this method for the delivery of siRNAs to folate receptor-expressing cells.

Molecular cloning and characterization of three novel lysozyme-like genes, predominantly expressed in the male reproductive system of humans, belonging to the c-type lysozyme/alpha-lactalbumin family.

Lysozymes, especially c-type lysozymes, are well-recognized bacteriolytic factors widely distributed in the animal kingdom and play a mainly protective role in host defense. The relatives of c-type lysozymes, alpha-lactalbumins, however, are only found in mammalian milk and possess a distinct biological function. These two proteins, having similar amino acid sequences, gene structure, and dimensional conformation, belong to the c-type lysozyme/alpha-lactalbumin family. Using human lysozyme as an information probe, we cloned four human cDNAs encoding homologues of human lysozyme; these were named LYZL2, LYZL4, LYZL6, and SPACA3 by the HUGO Gene Nomenclature Committee. Of these four, SPACA3 has been reported to code an intra-acrosomal sperm protein SLLP1. To our knowledge, the other three are reported here for the first time. Using Northern blot hybridization, including 16 different human tissues, we found that these four lysozyme-like genes were all highly expressed in the testis/epididymis. Further analysis of one, LYZL4, by in situ hybridization revealed that its mRNA was only detected in the epithelium of human epididymis, most abundantly in the caput, suggesting that LYZL4 plays a physiological role in male reproduction. By sequence analysis, we found that two essential catalytic residues of the human lysozyme were conserved in LYZL2 and LYZL6, whereas one site in LYZL4 and two sites in SPACA3 were replaced. The LYZL2, LYZL4, LYZL6, and SPACA3 genes were mapped to human chromosome 10p11.23, 3p21.33, 17q11.2, and 17q12, respectively, and displayed a similar genomic structure. Our data suggest that these four lysozyme-like genes, which have arisen from a common progenitor gene, play a major role in human reproduction.

Cloning, expression and subcellular localization of HN1 and HN1L genes, as well as characterization of their orthologs, defining an evolutionarily conserved gene family.

The present work reported the cloning and characterization of two novel human genes--HN1 (hematopoietic- and neurologic-expressed sequence 1) and HN1L (HN1-like gene) which are proposed to be involved in embryo development. HN1 is mapped on chromosome 17q25.2, with two transcripts (1.0 and 1.6 kb in length, respectively) due to alternative splicing. HN1 is expressed abundantly in testis and skeletal muscle among 16 human tissues, and it is localized in the nucleus indicated by GFP fusion expression. Western blot confirmed that HN1 encodes a 16.5-kDa protein. HN1L is on chromosome 16p13.3, with three splicing in the length of 2.0, 4.0 and 4.2 kb, respectively. HN1L is expressed in a variety of tissues such as liver, kidney, prostate, testis and uterus at varying levels. HN1L gene encodes a 20-kDa protein, which is localized in both the nucleus and cytoplasm. Fourteen of HN1 and sixteen of HN1L homologous genes in different species were determined and analyzed by BLAST searches. Silicon analyses of the 14 orthologous proteins of HN1 and 16 orthologous proteins of HN1L revealed that they share great conservation in vertebrate. Additionally, we identified nine pseudogenes of HN1 (six) and HN1L (three) in the genomes of the human, mouse and rat. Based on sequence alignments and phylogenetic analysis, all these homologous genes and pseudogenes were defined as a HN1 gene family.