Scholarly Journals--Published

  • Abu Shufian Ishtiaq Ahmed, Matilda H. C. Sheng, Kin-Hing William Lau, Sean M. Wilson, M. Daniel Wongworawat, Xiaolei Tang, Mahdis Ghahramanpouri, Antoine Nehme, Yi Xu, Amir Abdipour, Xiao-Bing Zhang, Samiksha Wasnik, and David J. Baylink (2022) Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation. Am J Physiol Cell Physiol. 322: C977–C99. A major cause of osteoporosis is impaired coupled bone formation. Mechanistically, both osteoclast-derived and bone-derived growth factors have been previously implicated. Here, we hypothesize that the release of bone calcium during osteoclastic bone resorption is essential for coupled bone formation. Osteoclastic resorption increases interstitial fluid calcium locally from the normal 1.8 mM up to 5 mM. MC3T3-E1 osteoprogenitor cells, cultured in a 3.6 mM calcium medium, demonstrated that calcium signaling stimulated osteogenic cell proliferation, differentiation, and migration. Calcium channel knockdown studies implicated calcium channels, Cav1.2, store-operated calcium entry (SOCE), and calcium-sensing receptor (CaSR) in regulating bone cell anabolic activities. MC3T3–E1 cells cultured in a 3.6 mM calcium medium expressed increased gene expression of Wnt signaling and growth factors platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and bone morphogenic protein-2 (BMP 2). Our coupling model of bone formation, the receptor activator of nuclear factor-κΒ ligand (RANKL)-treated mouse calvaria, confirmed the role of calcium signaling in coupled bone formation by exhibiting increased gene expression for osterix and osteocalcin. Critically, dual immunocytochemistry showed that RANKL treatment increased osterix-positive cells and increased fluorescence intensity of Cav1.2 and CaSR protein expression per osterix-positive cell. The above data established that calcium released by osteoclasts contributed to the regulation of coupled bone formation. CRISPR/Cas-9 knockout of Cav1.2 in osteoprogenitor cells cultured in basal calcium medium caused a >80% decrease in the expression of downstream osteogenic genes, emphasizing the large magnitude of the effect of calcium signaling. Thus, calcium signaling is a major regulator of coupled bone formation. (05/2022) (link)
  • Karina Mayagoitia, Andrew J Tolan, Shohali Shammi, Samuel D Shin, Jesus A Menchaca, Johnny D Figueroa, Christopher G Wilson, Denise L Bellinger, Abu Shufian Ishtiaq Ahmed, Salvador Soriano (2021) Loss of APP in mice increases thigmotaxis and is associated with elevated brain expression of IL-13 and IP-10/CXCL10. Physiology & Behavior. 240, 113533. Alzheimer's disease (AD) is a progressive neurodegenerative disorder that leads to memory loss and is often accompanied by increased anxiety. Although AD is a heterogeneous disease, dysregulation of inflammatory pathways is a consistent event. Interestingly, the amyloid precursor protein (APP), which is the source of the amyloid peptide Aβ, is also necessary for the efficient regulation of the innate immune response. Here, we hypothesize that loss of APP function in mice would lead to cognitive loss and anxiety behavior, both of which are typically present in AD, as well as changes in the expression of inflammatory mediators. To test this hypothesis, we performed open field, Y-maze and novel object recognition tests on 12–18-week-old male and female wildtype and AppKO mice to measure thigmotaxis, short-term spatial memory and long-term recognition memory. We then performed a quantitative multiplexed immunoassay to measure levels of 32 cytokines/chemokines associated with AD and anxiety. Our results showed that AppKO mice, compared to wildtype controls, experienced increased thigmotactic behavior but no memory impairments, and this phenotype correlated with increased IP-10 and IL-13 levels. Future studies will determine whether dysregulation of these inflammatory mediators contributes to pathogenesis in AD. (10/2021) (link)
  • Islam Osman, Kunzhe Dong, Xiuhua Kang, Luyi Yu, Fei Xu, Abu Shufian Ishtiaq Ahmed, Xiangqin He, Jian Shen, Guoqing Hu, Wei Zhang, Jiliang Zhou (2021) YAP1/TEAD1 upregulate platelet-derived growth factor receptor beta to promote vascular smooth muscle cell proliferation and neointima formation. JMCC. 156, P20-32. We have previously demonstrated that the transcription co-factor yes-associated protein 1 (YAP1) promotes vascular smooth muscle cell (VSMC) de-differentiation. Yet, the role and underlying mechanisms of YAP1 in neointima formation in vivo remain unclear. The goal of this study was to investigate the role of VSMC-expressed YAP1 in vascular injury-induced VSMC proliferation and delineate the mechanisms underlying its action. Experiments employing gain- or loss-of-function of YAP1 demonstrated that YAP1 promotes human VSMC proliferation. Mechanistically, we identified platelet-derived growth factor receptor beta (PDGFRB) as a novel YAP1 target gene that confers the YAP1-dependent hyper-proliferative effects in VSMCs. Furthermore, we identified TEA domain transcription factor 1 (TEAD1) as a key transcription factor that mediates YAP1-dependent PDGFRβ expression. ChIP assays demonstrated that TEAD1 is enriched at a PDGFRB gene enhancer. Luciferase reporter assays further demonstrated that YAP1 and TEAD1 co-operatively activate the PDGFRB enhancer. Consistent with these observations, we found that YAP1 expression is upregulated after arterial injury and correlates with PDGFRβ expression and VSMC proliferation in vivo. Using a novel inducible SM-specific Yap1 knockout mouse model, we found that the specific deletion of Yap1 in adult VSMCs is sufficient to attenuate arterial injury-induced neointima formation, largely due to inhibited PDGFRβ expression and VSMC proliferation. Our study unravels a novel mechanism by which YAP1/TEAD1 promote VSMC proliferation via transcriptional induction of PDGFRβ, thereby enhancing PDGF-BB downstream signaling and promoting neointima formation. (07/2021) (link)
  • Abu Ahmed, Zhe Zhong, Montry Suprono, Roberto Savignano, Holli Riter, Udochukwu Oyoyo, Alisa Wilson, Rebecca Reece, Jessica Kim, Eun-Hwi Cho, Robert Handysides, Paul Richardson, Joseph Caruso, Yiming Li (2021) Enhancement of peripheral seal of medical face masks using a 3D-printed custom frame. JADA. 152(7):542-550. (Corresponding author) Background During the COVID-19 pandemic, American Society for Testing and Materials level 3 and level 2 medical face masks (MFMs) have been used for most health care workers and even for the first responders owing to a shortage of N95 respirators. However, the MFMs lack effective peripheral seal, leading to concerns about their adequacy to block aerosol exposure for proper protection. The purpose of this study was to evaluate the peripheral seal of level 3 and level 2 MFMs with a 3-dimensional (3D-) printed custom frame. Methods Level 3 and level 2 MFMs were tested on 10 participants with and without a 3D-printed custom frame; the efficiency of mask peripheral seal was determined by means of quantitative fit testing using a PortaCount Fit Tester based on ambient aerosol condensation nuclei counter protocol. Results The 3D-printed custom frame significantly improved the peripheral seal of both level 3 and level 2 MFMs compared with the masks alone (P < .001). In addition, both level 3 and level 2 MFMs with the 3D-printed custom frame met the quantitative fit testing standard specified for N95 respirators. Practical Implications The 3D-printed custom frame over level 3 and level 2 MFMs can offer enhanced peripheral reduction of aerosols when using collapsible masks. With the shortage of N95 respirators, using the 3D-printed custom frame over a level 3 or level 2 MFM is considered a practical alternative to dental professionals. (07/2021) (link)
  • Montry S Suprono, John Won, Roberto Savignano, Zhe Zhong, Abu Ahmed, Gina Roque-Torres, Wu Zhang, Udochukwu Oyoyo, Paul Richardson, Joseph Caruso, Robert Handysides, Yiming Li (2021) A clinical investigation of dental evacuation systems in reducing aerosols. JADA. 152(6):455-462. Background: The route of transmission of severe acute respiratory syndrome coronavirus 2 has challenged dentistry to improve the safety for patients and the dental team during various treatment procedures. The purpose of this study was to evaluate and compare the effectiveness of dental evacuation systems in reducing aerosols during oral prophylactic procedures in a large clinical setting. Methods: This was a single-center, controlled clinical trial using a split-mouth design. A total of 93 student participants were recruited according to the inclusion and exclusion criteria. Aerosol samples were collected on blood agar plates that were placed around the clinic at 4 treatment periods: baseline, high-volume evacuation (HVE), combination (HVE and intraoral suction device), and posttreatment. Student operators were randomized to perform oral prophylaxis using ultrasonic scalers on 1 side of the mouth, using only HVE suction for the HVE treatment period and then with the addition of an intraoral suction device for the combination treatment period. Agar plates were collected after each period and incubated at 37 °C for 48 hours. Colony-forming unit (CFU) counts were determined using an automatic colony counter. Results: The use of a combination of devices resulted in significant reductions in CFUs compared with the use of the intraoral suction device alone (P < .001). The highest amounts of CFUs were found in the operating zone and on patients during both HVE and combination treatment periods. Conclusions: Within limitations of this study, the authors found significant reductions in the amount of microbial aerosols when both HVE and an intraoral suction device were used. (06/2021) (link)
  • Taiming Liu, Meijuan Zhang, George Mukosera, Daniel Borchardt, Qian Li, Trent Tipple, Abu Ahmed, Gordon Power, Arlin Blood (2019) L-NAME releases nitric oxide and potentiates subsequent nitroglycerin-mediated vasodilation. Redox Biology. 26:101238. L-NG-Nitro arginine methyl ester (L-NAME) has been widely applied for several decades in both basic and clinical research as an antagonist of nitric oxide synthase (NOS). Herein, we show that L-NAME slowly releases NO from its guanidino nitro group. Daily pretreatment of rats with L-NAME potentiated mesenteric vasodilation induced by nitrodilators such as nitroglycerin, but not by NO. Release of NO also occurred with the NOS-inactive enantiomer D-NAME, but not with L-arginine or another NOS inhibitor L-NMMA, consistent with the presence or absence of a nitro group in their structure and their nitrodilator-potentiating effects. Metabolic conversion of the nitro group to NO-related breakdown products was confirmed using isotopically-labeled L-NAME. Consistent with Fenton chemistry, transition metals and reactive oxygen species accelerated the release of NO from L-NAME. Both NO production from L-NAME and its nitrodilator-potentiating effects were augmented under inflammation. NO release by L-NAME can confound its intended NOS-inhibiting effects, possibly by contributing to a putative intracellular NO store in the vasculature. (06/2019) (link)
  • Abu Shufian Ishtiaq Ahmed, Kunzhe Dong, Tong Wen, Luyi Yu, Fei Xu, Xiuhua Kang, Guoqing Hu, Kristopher M. Bunting, Danielle Crethers, Hongyu Gao, Wei Zhang, Yunlong Liu, Ke Wen, Gautam Agarwal, Tetsuro Hirose, Shinichi Nakagawa, Almira Vazdarjanova, and Jiliang Zhou. (2018) The long noncoding RNA NEAT1 (nuclear paraspeckle assembly transcript 1) is critical for phenotypic switching of vascular smooth muscle cells. PNAS. 115 (37), E8660-E8667. In response to vascular injury, vascular smooth muscle cells (VSMCs) may switch from a contractile to a proliferative phenotype thereby contributing to neointima formation. Previous studies showed that the long noncoding RNA (lncRNA) NEAT1 is critical for paraspeckle formation and tumorigenesis by promoting cell proliferation and migration. However, the role of NEAT1 in VSMC phenotypic modulation is unknown. Herein we showed that NEAT1 expression was induced in VSMCs during phenotypic switching in vivo and in vitro. Silencing NEAT1 in VSMCs resulted in enhanced expression of SM-specific genes while attenuating VSMC proliferation and migration. Conversely, overexpression of NEAT1 in VSMCs had opposite effects. These in vitro findings were further supported by in vivo studies in which NEAT1 knockout mice exhibited significantly decreased neointima formation following vascular injury, due to attenuated VSMC proliferation. Mechanistic studies demonstrated that NEAT1 sequesters the key chromatin modifier WDR5 (WD Repeat Domain 5) from SM-specific gene loci, thereby initiating an epigenetic "off" state, resulting in down-regulation of SM-specific gene expression. Taken together, we demonstrated an unexpected role of the lncRNA NEAT1 in regulating phenotypic switching by repressing SM-contractile gene expression through an epigenetic regulatory mechanism. Our data suggest that NEAT1 is a therapeutic target for treating occlusive vascular diseases. (08/2018) (link)
  • George T. Mukosera, Taiming Liu, Abu Shufian Ishtiaq Ahmed, Qian Li, Matilda H.-C. Sheng, Trent E. Tipple, David J. Baylink, Gordon G. Power, and Arlin B. Blood. (2018) Detection of Dinitrosyl Iron Complexes by Ozone-based Chemiluminescence. Nitric Oxide. 79:57-67. Dinitrosyl iron complexes (DNICs) are important intermediates in the metabolism of nitric oxide (NO). They have been considered to be NO storage adducts able to release NO, scavengers of excess NO during inflammatory hypotensive shock, and mediators of apoptosis in cancer cells, among many other functions. Currently, all studies of DNICs in biological matrices use electron paramagnetic resonance (EPR) for both detection and quantification. EPR is limited, however, by its ability to detect only paramagnetic mononuclear DNICs even though EPR-silent binuclear are likely to be prevalent. Furthermore, physiological concentrations of mononuclear DNICs are usually lower than the EPR detection limit (1 μM). We have thus developed a chemiluminescence-based method for the selective detection of both DNIC forms at physiological, pathophysiological, and pharmacologic conditions. We have also demonstrated the use of the new method in detecting DNIC formation in the presence of nitrite and nitrosothiols within biological fluids and tissue. This new method, which can be used alone or in tandem with EPR, has the potential to offer insight about the involvement of DNICs in many NO-dependent pathways. (07/2018) (link)
  • Matilda H.-C. Sheng, Kin-Hing William Lau, Ram Lakhan, Abu Shufian Ishtiaq Ahmed, Charles H. Rundle, Patra Biswanath, and David J. Baylink (2017) Unique Regenerative Mechanism to Replace Bone Lost During Dietary Bone Depletion in Weanling Mice. Endocrinology. 158(4):714-729. The present study was undertaken to determine the mechanism whereby calcitropic hormones and mesenchymal stem cell progeny changes are involved in bone repletion, a regenerative bone process that restores the bone lost to calcium deficiency. To initiate depletion, weanling mice with a mixed C57BL/6 (75%) and CD1 (25%) genetic background were fed a calcium-deficient diet (0.01%) for 14 days. For repletion, the mice were fed a control diet containing 1.2% calcium for 14 days. Depletion decreased plasma calcium and increased plasma parathyroid hormone, 1,25(OH)2D (calcitriol), and C-terminal telopeptide of type I collagen. These plasma parameters quickly returned toward normal on repletion. The trabecular bone volume and connectivity decreased drastically during depletion but were completely restored by the end of repletion. This bone repletion process largely resulted from the development of new bone formation. When bromodeoxyuridine (BrdU) was administered in the middle of depletion for 3 days and examined by fluorescence-activated cell sorting at 7 days into repletion, substantial increases in BrdU incorporation were seen in several CD105 subsets of cells of osteoblastic lineage. When BrdU was administered on days 1 to 3 of repletion and examined 11 days later, no increases in BrdU were seen in these subsets. Additionally, osteocytes that stained positively for BrdU were increased during depletion. In conclusion, the results of the present study have established a unique regenerative mechanism to initiate bone repair during the bone insult. Calcium homeostatic mechanisms and the bone repletion mechanism are opposing functions but are simultaneously orchestrated such that both endpoints are optimized. These results have potential clinical relevance for disease entities such as type 2 osteoporosis. (04/2017) (link)
  • Abu Shufian Ishtiaq Ahmed, Matilda H.-C. Sheng, Samiksha Wasnik, David J. Baylink, and Kin-Hing William Lau (2017) The effect of aging on stem cells. World Journal of Experimental Medicine. 20;7(1):1-10. Pluripotent stem cells have the remarkable self-renewal ability and are capable of differentiating into multiple diverse cells. There is increasing evidence that the aging process can have adverse effects on stem cells. As stem cells age, their renewal ability deteriorates and their ability to differentiate into the various cell types is altered. Accordingly, it is suggested aging-induced deterioration of stem cell functions may play a key role in the pathophysiology of the various aging-associated disorders. Understanding the role of the aging process in deterioration of stem cell function is crucial, not only in understanding the pathophysiology of aging-associated disorders, but also in future development of novel effective stem cell-based therapies to treat aging-associated diseases. This review article first focuses on the basis of the various aging disease-related stem cell dysfunction. It then addresses the several concepts on the potential mechanism that causes aging-related stem cell dysfunction. It also briefly discusses the current potential therapies under development for aging-associated stem cell defects. (02/2017) (link)
  • Juan Zhou, Longfei Wang, Mengxia Zuo, Xiaojing Wang, Abu Shufian Ishtiaq Ahmed, Qiuyun Chen, and Qing K. Wang (2016) Cardiac sodium channel regulator MOG1 regulates cardiac morphogenesis and rhythm.  Scientific Reports. 6:21538. MOG1 was initially identified as a protein that interacts with the small GTPase Ran involved in transport of macromolecules into and out of the nucleus. In addition, we have established that MOG1 interacts with the cardiac sodium channel Nav1.5 and regulates cell surface trafficking of Nav1.5. Here we used zebrafish as a model system to study the in vivo physiological role of MOG1. Knockdown of mog1 expression in zebrafish embryos significantly decreased the heart rate (HR). Consistently, the HR increases in embryos with over-expression of human MOG1. Compared with wild type MOG1 or control EGFP, mutant MOG1 with mutation E83D associated with Brugada syndrome significantly decreases the HR. Interestingly, knockdown of mog1 resulted in abnormal cardiac looping during embryogenesis. Mechanistically, knockdown of mog1 decreases expression of hcn4 involved in the regulation of the HR, and reduces expression of nkx2.5gata4 and hand2 involved in cardiac morphogenesis. These data for the first time revealed a novel role that MOG1, a nucleocytoplasmic transport protein, plays in cardiac physiology and development. (02/2016) (link)
  • Fei Xu, Abu Shufian Ishtiaq Ahmed, Xiuhua Kang, Guoqing Hu, Fang Liu, Wei Zhang, Jiliang Zhou (2015) MicroRNA-15b/16 Attenuates Vascular Neointima Formation by Promoting the Contractile Phenotype of Vascular Smooth Muscle Through Targeting YAP. Arteriosclerosis Thrombosis, and Vascular Biology. 35:2145-2152. Objective: To investigate the functional role of the microRNA (miR)-15b/16 in vascular smooth muscle (SM) phenotypic modulation. Approach and Results: We found that miR-15b/16 is one of the most abundant mRs expressed in contractile vascular smooth muscle cells (VSMCs). However, when contractile VSMCs get converted to a synthetic phenotype, miR-15b/16 expression is significantly reduced. Knocking down endogenous miR-15b/16 in VSMCs attenuates SM-specific gene expression but promotes VSMC proliferation and migration. Conversely, overexpression of miR-15b/16 promotes SM contractile gene expression while attenuating VSMC migration and proliferation. Consistent with this, overexpression of miR-15b/16 in a rat carotid balloon injury model markedly attenuates injury-induced SM dedifferentiation and neointima formation. Mechanistically, we identified the potent oncoprotein yes-associated protein (YAP) as a downstream target of miR-15b/16 in VSMCs. Reporter assays validated that miR-15b/16 targets YAP's 3' untranslated region. Moreover, overexpression of miR-15b/16 significantly represses YAP expression, whereas conversely, depletion of endogenous miR-15b/16 results in upregulation of YAP expression. Conclusions: These results indicate that miR-15b/16 plays a critical role in SM phenotypic modulation at least partly through targeting YAP. Restoring expression of miR-15b/16 would be a potential therapeutic approach for treatment of proliferative vascular diseases. (10/2015) (link)
  • Damien N. Barnette, Alexia Hulin, Abu Shufian Ishtiaq Ahmed, Alain C. Colige, Mohamad Azhar and Joy Lincoln (2013) Tgfb-Smad and MAPK signaling mediate scleraxis and proteoglycan expression in heart valves. Journal of Molecular and Cellular Cardiology. 65: 137-146. Mature heart valves are complex structures consisting of three highly organized extracellular matrix layers primarily composed of collagens, proteoglycans and elastin. Collectively, these diverse matrix components provide all the necessary biomechanical properties for valve function throughout life. In contrast to healthy valves, myxomatous valve disease is the most common cause of mitral valve prolapse in the human population and is characterized by an abnormal abundance of proteoglycans within the valve tri-laminar structure. Despite the clinical significance, the etiology of this phenotype is not known. Scleraxis (Scx) is a basic-helix-loop-helix transcription factor that we previously showed to be required for establishing heart valve structure during remodeling stages of valvulogenesis. In this study, we report that remodeling heart valves from Scx null mice express decreased levels of proteoglycans, particularly chondroitin sulfate proteoglycans (CSPGs), while overexpression in embryonic avian valve precursor cells and adult porcine valve interstitial cells increases CSPGs. Using these systems we further identify that Scx is positively regulated by canonical Tgfβ2 signaling during this process and this is attenuated by MAPK activity. Finally, we show that Scx is increased in myxomatous valves from human patients and mouse models, and overexpression in human mitral valve interstitial cells modestly increases proteoglycan expression consistent with myxomatous mitral valve phenotypes. Together, these studies identify an important role for Scx in regulating proteoglycans in embryonic and mature valve cells and suggest that imbalanced regulation could influence myxomatous pathogenesis. (12/2014) (link)
  • Abu Shufian Ishtiaq Ahmed, Gracelin C. Bose, Li Huang, and Mohamad Azhar (2014) Generation of mice carrying a knockout-first and conditional-ready allele of transforming growth factor beta2 gene. Genesis. 52(9): 817-26. Transforming growth factor beta2 (TGFβ2) is a multifunctional protein which is expressed in several embryonic and adult organs. TGFB2 mutations can cause Loeys Dietz syndrome, and its dysregulation is involved in cardiovascular, skeletal, ocular and neuromuscular diseases, osteoarthritis, tissue fibrosis, and various forms of cancer. TGFβ2 is involved in cell growth, apoptosis, cell migration, cell differentiation, cell-matrix remodeling, epithelial-mesenchymal transition, and wound healing in a highly context-dependent and tissue-specific manner. Tgfb2−/− mice die perinatally from congenital heart disease, precluding functional studies in adults. Here, we have generated mice harboring Tgfb2βgeo (knockout-first lacZ-tagged insertion) gene-trap allele and Tgfb2flox conditional allele. Tgfb2βgeo/βgeo or Tgfb2βgeo/− mice died at perinatal stage from the same congenital heart defects as Tgfb2−/− mice. β-galactosidase staining successfully detected Tgfb2 expression in the heterozygous Tgfb2βgeo fetal tissue sections. Tgfb2flox mice were produced by crossing the Tgfb2+/βgeo mice with the FLPeR mice. Tgfb2flox/− mice were viable. Tgfb2 conditional knockout (Tgfb2cko/−) fetuses were generated by crossing of Tgfb2flox/− mice with Tgfb2+/−;EIIaCre mice. Systemic Tgfb2cko/− embryos developed cardiac defects which resembled the Tgfb2βgeo/βgeo, Tgfb2βgeo/−, and Tgfb2−/− fetuses. In conclusion, Tgfb2βgeo and Tgfb2flox mice are novel mouse strains which will be useful for investigating the tissue specific expression and function of TGFβ2 in embryonic development, adult organs, and disease pathogenesis and cancer. (06/2014) (link)
  • Abu Shufian Ishtiaq Ahmed, Feng Xiong, Shao-Chen Pang, Mu-Dan He, Michael J. Waters, Zuo-Yan Zhu and Yong-Hua Sun (2011) Activation of GH signaling and GH-independent stimulation of growth in zebrafish by introduction of a constitutively activated GHR construct. Transgenic Research. 20(3): 557-567. Growth hormone (GH) gene transfer can markedly increase growth in transgenic fish. In the present study we have developed a transcriptional assay to evaluate GH-signal activation (GHSA) in zebrafish embryos. By analyzing the transcription of c-fos and igf1, and the promoter activity of spi2.1, in zebrafish embryos injected with different constructs, we found that overexpression of either GH or growth hormone receptor (GHR) resulted in GHSA, while a synergetic overexpression of GH and GHR gave greater activation. Conversely, overexpression of a C-terminal truncated dominant-negative GHR (ΔC-GHR) efficiently blocked GHSA epistatic to GH overexpression, demonstrating the requirement for a full GHR homodimer in signaling. In view of the importance of signal-competent GHR dimerization by extracellular GH, we introduced into zebrafish embryos a constitutively activated GHR (CA-GHR) construct, which protein products constitutively dimerize the GHR productively by Jun-zippers to activate downstream signaling in vitro. Importantly, overexpression of CA-GHR led to markedly higher level of GHSA than the synergetic overexpression of GH and GHR. CA-GHR transgenic zebrafish were then studied in a growth trial. The transgenic zebrafish showed higher growth rate than the control fish, which was not achievable by GH transgenesis in these zebrafish. Our study demonstrates GH-independent growth by CA-GHR in vivo which bypasses normal IGF-1 feedback control of GH secretion. This provides a novel means of producing growth enhanced transgenic animals based on molecular protein design. (08/2010) (link)

Books and Chapters

  • Samiksha Wasnik, Wanqiu Chen, Abu Shufian Ishtiaq Ahmed, Xiao-Bing Zhang, Xiaolei Tang, and David J. Baylink (2017) "'HSC Niche: Regulation of Mobilization and Homing" in Ajaykumar Vishwakarma and Jeff Karp (Eds.) Biology and Engineering of Stem Cell Niches. United States: Academic Press, Elsevier Inc. 63-70. (03/2017) (link)