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1.
Cureus ; 16(4): e59096, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38803782

ABSTRACT

While the coronavirus disease 2019 (COVID-19) pandemic has impacted medication adherence and consultation patterns, its effects on the medical practice and dispensary separation system of Japan remain unclear. Thus, the utilization of the medication record handbook (MRH) in both medical and dental areas remains uncertain. This study uses the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB); we analyzed the separation of medication prescription and dispensing in both medicine and dentistry, as well as estimated how much drug information is shared by utilizing a patient-carried MRH. The external prescription (EP) rate was used as the main indicator. We then analyzed the MRH utilization rate during outpatient medication guidance. During the pandemic, there was no distinctive change in the rate of EPs in both medicine and dentistry. Furthermore, an analysis between EPs, medical internal prescriptions (IPs), and dental IPs relative to the MRH utilization rate revealed significant correlations between EPs and medical IPs as well as medical and dental IPs. Conversely, no significant correlation was found between EPs and dental IPs. Therefore, our results suggest that active MRH implementation within healthcare facilities may lead to an increase in its utilization in dentistry.

2.
Cureus ; 16(2): e55140, 2024 Feb.
Article in English | MEDLINE | ID: mdl-38558741

ABSTRACT

Cerebral vasospasm is a frequent complication of subarachnoid hemorrhage. We report a case of chronic subdural hematoma complicated by cerebral vasospasm after burr hole evacuation. A 74-year-old woman underwent burr hole evacuation of a chronic subdural hematoma. She developed left hemiparesis and disturbance of consciousness on postoperative day 3. Magnetic resonance imaging showed a right parietal infarct and decreased cerebral blood flow signal in the right middle cerebral artery territory. Digital subtraction angiography showed multiple segmental narrowings of the right middle cerebral artery. Her neurological symptoms recovered with conservative treatment. Follow-up angiography showed improvement in the arterial narrowing, which finally led to a diagnosis of cerebral vasospasm. Cerebral vasospasm can occur after burr hole evacuation of chronic subdural hematoma. Magnetic resonance angiography is useful for determining the cause of postoperative neurological worsening in chronic subdural hematoma patients.

3.
Radiol Case Rep ; 19(3): 974-977, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38204933

ABSTRACT

Hemodynamic factors are associated with the progression of cerebral aneurysms. We report a 78-year-old woman with an anterior inferior cerebellar artery aneurysm and proximal stenosis of the anterior inferior cerebellar and basilar arteries. The aneurysm exhibited growth on annual follow-up imaging. Aneurysmal rupture occurred 4 years after diagnosis. Coil embolization resulted in aneurysm occlusion with parent artery preservation. Aneurysms adjacent to a more proximal region of severe stenosis in the parent vessel should be considered at high risk for growth or rupture. Such aneurysms require careful monitoring. Particular attention should be paid to posterior circulation aneurysms that occur at anatomically vulnerable sites.

4.
Ocul Surf ; 29: 486-494, 2023 07.
Article in English | MEDLINE | ID: mdl-37453535

ABSTRACT

PURPOSE: To investigate the role of Wnt/ß-catenin signaling in mouse eyelid development. METHODS: Wnt/ß-catenin signaling was disrupted by deleting supraorbital mesenchymal ß-catenin or epithelial Wls. p63 was removed to determine whether the expression of Wnts is affected. The eyelid morphology was examined at different stages. Proliferation, apoptosis, and expression of Wnt ligands and their target genes were analyzed via immunofluorescence staining, TUNEL assay, and in situ hybridization. RESULTS: Deletion of ß-catenin in supraorbital mesenchyme abolishes eyelid growth by causing decreased proliferation in supraorbital epithelium and underlying mesenchyme. Inhibition of Wnt secretion by deleting Wls in supraorbital epithelium results in failure of eyelid development, similar to the effects of deleting mesenchymal ß-catenin. Knockout of p63 results in formation of hypoplastic eyelids and reduced expression of several Wnt ligands in eyelid epithelium. CONCLUSIONS: Epithelial Wnt ligands activate mesenchymal Wnt/ß-catenin signaling to control eyelid growth and their expression is partially regulated by p63.


Subject(s)
Wnt Signaling Pathway , beta Catenin , Mice , Animals , beta Catenin/genetics , beta Catenin/metabolism , Ligands , Mice, Knockout , Epithelium/metabolism , Wnt Signaling Pathway/genetics , Cell Proliferation
5.
Life (Basel) ; 13(3)2023 Mar 03.
Article in English | MEDLINE | ID: mdl-36983843

ABSTRACT

The field of epithelial stem cell development has been irrevocably shaped by the work of American scientist Howard Green, whose breakthroughs in stem cell culture methods translated to therapeutic practice. In this review, we chronicle the milestones that propelled the field of regenerative medicine of the skin forward over the last fifty years. We detail the early discoveries made by Green and his collaborators, highlight clinical cases that made life-saving use of his findings, and discuss the accomplishments of other scientists who later innovated upon his discoveries.

6.
Sci Rep ; 13(1): 4532, 2023 03 20.
Article in English | MEDLINE | ID: mdl-36941290

ABSTRACT

The surface of the middle ear is composed of the tympanic membrane (TM) and the middle ear mucosa (MEM). A number of diseases and conditions such as otitis media, middle ear cholesteatoma, and perforation of the TM have been reported to cause dysfunction of the middle ear, ultimately leading to high-frequency hearing loss. Despite its importance in repairing the damaged tissues, the stem/progenitor cells of the TM and the MEM epithelia remains largely uncharacterized due, in part, to the lack of an optimal methodology to expand and maintain stem/progenitor cells long-term. Here, we show that suppression of TGF-ß signaling in a low Ca2+ condition enables long-term proliferation of p63-positive epithelial stem/progenitor cells of the TM and the MEM while avoiding their malignant transformation. Indeed, our data show that the expanded TM and MEM stem/progenitor cells respond to Ca2+ stimulation and differentiate into the mature epithelial cell lineages marked by cytokeratin (CK) 1/8/18 or Bpifa1, respectively. These results will allow us to expand epithelial stem/progenitor cells of the TM and MEM in quantity for large-scale analyses and will enhance the use of mouse models in developing stem cell-mediated therapeutic strategies for the treatment of middle ear diseases and conditions.


Subject(s)
Tympanic Membrane Perforation , Tympanic Membrane , Mice , Animals , Ear, Middle , Stem Cells , Mucous Membrane , Transforming Growth Factor beta , Cell Proliferation , Tympanic Membrane Perforation/etiology , Glycoproteins , Phosphoproteins
7.
No Shinkei Geka ; 49(6): 1198-1210, 2021 Nov.
Article in Japanese | MEDLINE | ID: mdl-34879340

ABSTRACT

Anterior cervical foraminotomy is a motion-preserving and precise decompressing surgery with minimal bone removal. As preserving the motion segment and maximizing decompression are contradictory concepts, proficiency is needed to balance these requirements. Anatomical knowledge and good intraoperative orientation are essential to reach the nerve roots accurately in a narrow surgical field.


Subject(s)
Foraminotomy , Radiculopathy , Cervical Vertebrae/diagnostic imaging , Cervical Vertebrae/surgery , Decompression, Surgical , Humans , Radiculopathy/surgery
8.
J Neurosurg Case Lessons ; 2(14)2021 Oct 04.
Article in English | MEDLINE | ID: mdl-36131572

ABSTRACT

BACKGROUND: Idiopathic spinal cord herniation (ISCH) is very rare. Some reports have described postoperative ventral cerebrospinal fluid (CSF) collections in patients with ISCH; however, such collections are asymptomatic in most patients, and there is no consensus regarding whether they are part of the natural history or a complication. OBSERVATIONS: A 30-year-old man with ISCH underwent direct closure of a duplicated dura mater. Eight months postoperatively, he developed reworsening of right lower limb paresis and new severe right arm pain and paresis. Three-dimensional magnetic resonance imaging revealed ventral CSF collections, which the authors judged as the responsible lesions. The authors initially considered these collections to be present in the epidural space, extradurally compressing the dural sac and resulting in myelopathy. An epidural blood patch failed; however, a CSF drainage test resulted in dramatic improvement. The authors therefore determined that the CSF collections were located in the interdural space, not the epidural space. A lumboperitoneal (LP) shunt was performed to reduce the CSF pressure. The patient's symptoms improved immediately postoperatively. He had developed no recurrence of symptoms 6 months after surgery. LESSONS: Ventral interdural CSF collections after ISCH surgery can cause reworsening of myelopathy and may be cured by a LP shunt to control CSF pressure.

9.
Methods Mol Biol ; 2109: 1-22, 2020.
Article in English | MEDLINE | ID: mdl-31489602

ABSTRACT

Although mouse models have been used as an essential tool for studying the physiology and diseases of the skin, propagation of mouse primary epidermal keratinocytes remains challenging. In this chapter, we introduce the simplest, at least to our knowledge, protocol that enables long-term expansion of p63+ mouse epidermal keratinocytes in low Ca2+ media without the need of progenitor cell-purification steps or support by a feeder cell layer. Pharmacological inhibition of TGF-ß signaling in crude preparations of mouse epidermis robustly increases proliferative capacity of p63+ epidermal progenitor cells, while preserving their ability to differentiate. Suppression of TGF-ß signaling also permits p63+ epidermal keratinocytes to form macroscopically large clones in 3T3-J2 feeder cell co-culture. Suppression of TGF-ß signaling also enhances the clonal growth of human keratinocytes in co-culture with a variety of feeder cells. This simple and efficient approach will not only facilitate the use of mouse models by providing p63+ primary epidermal keratinocytes in quantity but also significantly reduce the time needed for preparing the customized skin grafts in Green method.


Subject(s)
Calcium/metabolism , Cell Culture Techniques/methods , Keratinocytes/cytology , Trans-Activators/metabolism , Transcription Factors/metabolism , Tumor Suppressor Proteins/metabolism , 3T3 Cells , Animals , Cell Differentiation , Cell Proliferation , Cells, Cultured , Coculture Techniques , Culture Media/chemistry , Feeder Cells/cytology , Humans , Keratinocytes/metabolism , Mice , Signal Transduction , Transforming Growth Factor beta/metabolism
10.
Methods Mol Biol ; 1993: 15-31, 2019.
Article in English | MEDLINE | ID: mdl-31148075

ABSTRACT

Co-culture of human epidermal keratinocytes with mouse 3T3-J2 feeder cells, developed by Green and colleagues, has been used worldwide to generate skin autografts since the early 1980s. In addition, co-culture with 3T3-J2 cells has served as a fundamental tool in skin stem cell biology as it allows the evaluation of self-renewal capacity of epidermal stem cells. This chapter describes a recent improvement in the Green method to promote further the expansion of human epidermal keratinocytes utilizing a small-molecule inhibitor of TGF-ß signaling. This new protocol enables more rapid expansion of human epidermal keratinocytes in co-culture with not only 3T3-J2 cells but also other feeder cells including human dermal fibroblasts and human preadipocytes, two major alternatives to 3T3-J2 cells, with a long-term goal of developing customized skin autografts.


Subject(s)
Coculture Techniques/methods , Feeder Cells , Keratinocytes/metabolism , Animals , Autografts , Epidermal Cells/metabolism , Humans , Mice , Signal Transduction , Skin Transplantation , Stem Cells , Transforming Growth Factor beta/metabolism
11.
Methods Mol Biol ; 1993: 47-59, 2019.
Article in English | MEDLINE | ID: mdl-31148077

ABSTRACT

Mouse models have been used to study the physiology and pathogenesis of the skin. However, propagation of mouse primary epidermal keratinocytes remains challenging. In this chapter, we introduce a newly developed protocol that enables long-term expansion of p63+ mouse epidermal keratinocytes in low-Ca2+ media without the need of progenitor cell purification steps or support by a feeder cell layer. Pharmacological inhibition of TGF-ß signaling in crude preparations of mouse epidermis robustly increases proliferative capacity of p63+ epidermal progenitor cells while preserving their ability to differentiate. Suppression of TGF-ß signaling also permits p63+ epidermal keratinocytes to form macroscopically large clones in 3T3-J2 feeder cell co-culture. This simple and efficient approach will facilitate the use of mouse models by providing p63+ primary epidermal keratinocytes in quantity.


Subject(s)
Culture Techniques/methods , Keratinocytes/metabolism , Signal Transduction/drug effects , Animals , Coculture Techniques , Epidermal Cells/drug effects , Epidermal Cells/metabolism , Feeder Cells , Keratinocytes/drug effects , Mice , Transforming Growth Factor beta/metabolism
12.
Sci Rep ; 7(1): 6089, 2017 07 20.
Article in English | MEDLINE | ID: mdl-28729719

ABSTRACT

Mouse models have been used to provide primary cells to study physiology and pathogenesis of epithelia. However, highly efficient simple approaches to propagate mouse primary epithelial cells remain challenging. Here, we show that pharmacological inhibition of TGF-ß signaling enables long-term expansion of p63+ epithelial progenitor cells in low Ca2+ media without the need of progenitor cell-purification steps or support by a feeder cell layer. We find that TGF-ß signaling is operative in mouse primary keratinocytes in conventional cultures as determined by the nuclear Smad2/3 localization. Accordingly, TGF-ß signaling inhibition in crude preparations of mouse epidermis robustly increases proliferative capacity of p63+ epidermal progenitor cells, while preserving their ability of differentiation in response to Ca2+ stimulation. Notably, inhibition of TGF-ß signaling also enriches and expands other p63+ epithelial progenitor cells in primary crude cultures of multiple epithelia, including the cornea, oral and lingual epithelia, salivary gland, esophagus, thymus, and bladder. We anticipate that this simple and efficient approach will facilitate the use of mouse models for studying a wide range of epithelia by providing highly enriched populations of diverse p63+ epithelial progenitor cells in quantity.


Subject(s)
Epithelial Cells/metabolism , Signal Transduction , Stem Cells/cytology , Stem Cells/metabolism , Transforming Growth Factor beta/metabolism , Animals , Cell Differentiation , Cell Line , Cell Proliferation , Cell Self Renewal/genetics , Epidermal Cells/cytology , Epidermal Cells/metabolism , Mice , Phosphoproteins/metabolism , Trans-Activators/metabolism
13.
Wound Repair Regen ; 25(3): 526-531, 2017 05.
Article in English | MEDLINE | ID: mdl-28437853

ABSTRACT

Cultured epidermal autografts have been used worldwide since 1981 for patients with extensive third-degree burn wounds and limited skin donor sites. Despite significant progress in techniques toward improving clinical outcome of skin grafts, the long in vitro preparation time of cultured autografts has remained a major factor limiting its widespread use. Here, we show that pharmacological inhibition of TGF-ß signaling promotes the expansion of human epidermal keratinocytes (HEKs) with high proliferative potential in co-cultures with both murine 3T3-J2 cells and human feeder cells, including dermal fibroblasts and preadipocytes. In contrast, TGF-ß signaling inhibition does not enhance the growth of HEKs in a serum- and feeder-free condition, an alternative approach to propagate HEKs for subsequent autograft production. Our results have important implications for the use of TGF-ß signaling inhibition as a viable therapeutic strategy for improving Green's methodology and for more efficient production of customized skin autografts with human feeder cells.


Subject(s)
Coculture Techniques , Epidermal Cells , Feeder Cells/cytology , Keratinocytes/cytology , Keratinocytes/drug effects , Pyrazoles/pharmacology , Pyridines/pharmacology , Signal Transduction/drug effects , Transforming Growth Factor beta/antagonists & inhibitors , 3T3 Cells , Animals , Disease Models, Animal , Epidermis/drug effects , Feeder Cells/drug effects , Humans , Mice , Skin Transplantation/methods
15.
Vet Dermatol ; 26(4): 213-e47, 2015 Aug.
Article in English | MEDLINE | ID: mdl-25963063

ABSTRACT

BACKGROUND: The limited characterization of equine skin, eye and hoof epithelial stem cell (ESC) and differentiation markers impedes the investigation of the physiology and pathophysiology of these tissues. HYPOTHESIS/OBJECTIVES: To characterize ESC and differentiation marker expression in epithelial tissues of the equine eye, haired skin and hoof capsule. METHODS: Indirect immunofluorescence microscopy and immunoblotting were used to detect expression and tissue localization of keratin (K) isoforms K3, K10, K14 and K124, the transcription factor p63 (a marker of ESCs) and phosphorylated p63 [pp63; a marker of ESC transition to transit-amplifying (TA) cell] in epithelial tissues of the foot (haired skin, hoof coronet and hoof lamellae) and the eye (limbus and cornea). RESULTS: Expression of K14 was restricted to the basal layer of epidermal lamellae and to basal and adjacent suprabasal layers of the haired skin, coronet and corneal limbus. Coronary and lamellar epidermis was negative for both K3 and K10, which were expressed in the cornea/limbus epithelium and haired skin epidermis, respectively. Variable expression of p63 with relatively low to high levels of phosphorylation was detected in individual basal and suprabasal cells of all epithelial tissues examined. CONCLUSIONS: To the best of the author's knowledge, this is the first report of the characterization of tissue-specific keratin marker expression and the localization of putative epithelial progenitor cell populations, including ESCs (high p63 expression with low pp63 levels) and TA cells (high expression of both p63 and pp63), in the horse. These results will aid further investigation of epidermal and corneal epithelial biology and regenerative therapies in horses.


Subject(s)
Cell Differentiation/physiology , Cornea/cytology , Hoof and Claw/cytology , Horses/anatomy & histology , Skin/cytology , Stem Cells/physiology , Animals , Antigens, Differentiation/metabolism , Cornea/metabolism , Epithelium/metabolism , Female , Fluorescent Antibody Technique, Indirect , Hoof and Claw/metabolism , Horses/metabolism , Immunoblotting , Keratins/metabolism , Male , Skin/metabolism , Stem Cells/metabolism
16.
Development ; 142(2): 282-90, 2015 Jan 15.
Article in English | MEDLINE | ID: mdl-25503409

ABSTRACT

The transcription factor p63 (Trp63) plays a key role in homeostasis and regeneration of the skin. The p63 gene is transcribed from dual promoters, generating TAp63 isoforms with growth suppressive functions and dominant-negative ΔNp63 isoforms with opposing properties. p63 also encodes multiple carboxy (C)-terminal variants. Although mutations of C-terminal variants have been linked to the pathogenesis of p63-associated ectodermal disorders, the physiological role of the p63 C-terminus is poorly understood. We report here that deletion of the p63 C-terminus in mice leads to ectodermal malformation and hypoplasia, accompanied by a reduced proliferative capacity of epidermal progenitor cells. Notably, unlike the p63-null condition, we find that p63 C-terminus deficiency promotes expression of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1) (Cdkn1a), a factor associated with reduced proliferative capacity of both hematopoietic and neuronal stem cells. These data suggest that the p63 C-terminus plays a key role in the cell cycle progression required to maintain the proliferative potential of stem cells of many different lineages. Mechanistically, we show that loss of Cα, the predominant C-terminal p63 variant in epithelia, promotes the transcriptional activity of TAp63 and also impairs the dominant-negative activity of ΔNp63, thereby controlling p21(Waf1/Cip1) expression. We propose that the p63 C-terminus links cell cycle control and the proliferative potential of epidermal progenitor cells via mechanisms that equilibrate TAp63 and ΔNp63 isoform function.


Subject(s)
Cell Cycle Proteins/metabolism , Cell Proliferation/physiology , Epidermal Cells , Phosphoproteins/metabolism , Stem Cells/physiology , Trans-Activators/metabolism , Animals , Blotting, Southern , Blotting, Western , Bromodeoxyuridine , DNA Primers/genetics , Immunohistochemistry , Mice , Mice, Knockout , Phosphoproteins/genetics , Protein Isoforms/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Trans-Activators/genetics
17.
Gene Expr Patterns ; 15(1): 21-30, 2014 May.
Article in English | MEDLINE | ID: mdl-24681206

ABSTRACT

The Wnt signaling pathway is essential for cell fate decisions during embryonic development as well as for homeostasis after birth. Dapper antagonist of catenin-1 (Dact1) plays an important role during embryogenesis by regulating Wnt signaling pathways. Consequently, targeted disruption of the Dact1 gene in mice leads to perinatal lethality due to severe developmental defects involving the central nervous system, genitourinary system and distal digestive tract. However, the expression and potential function of Dact1 in other tissues during development and postnatal life have not been well studied. Here, we have generated reporter mice in which LacZ expression is driven by the Dact1 gene promoter and characterized Dact1-LacZ expression in embryos and adult tissues. Our data show that while Dact1-LacZ is expressed in multiple mesoderm- and neuroectoderm-derived tissues during development, high expression of Dact1-LacZ is restricted to a small subset of adult tissues, including the brain, eye, heart, and some reproductive organs. These results will serve as a basis for future investigation of Dact1 function in Wnt-mediated organogenesis and tissue homeostasis.


Subject(s)
Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/metabolism , Lac Operon , Animals , Embryo, Mammalian/metabolism , Female , Gene Expression Regulation , Genes, Reporter , Genetic Vectors/genetics , Genetic Vectors/metabolism , Male , Mice , Organ Specificity , Promoter Regions, Genetic , RNA-Binding Proteins
18.
Exp Dermatol ; 22(5): 374-6, 2013 May.
Article in English | MEDLINE | ID: mdl-23614751

ABSTRACT

The transcription factor p63 plays an essential role in maintaining the proliferative potential of epidermal stem cells. We have shown recently that under homoeostatic conditions, phosphorylation of p63 increases during the early transition of stem cells to transit-amplifying cells in human epidermis. However, how p63 phosphorylation relates to the regenerative processes during wound healing remains unknown. In this study, we characterize epidermal cells that contribute to wound repair in mouse models using phosphorylated p63 as a marker for stem cell differentiation. Our studies reveal that epidermal progenitors with high p63 phosphorylation preferentially expand in response to wounding in both full-thickness wound and surface injury models. As phosphorylated p63 levels inversely correlate with the proliferative potential of epidermal progenitors, p63 phosphorylation may serve as a therapeutic target to modulate the function of these regenerative cells during wound healing.


Subject(s)
Epidermal Cells , Epidermis/injuries , Membrane Proteins/metabolism , Stem Cells/cytology , Stem Cells/metabolism , Wound Healing/physiology , Animals , Cell Proliferation , Disease Models, Animal , Epidermis/metabolism , Female , Mice , Mice, Inbred C57BL , Phosphorylation/physiology
19.
Adv Wound Care (New Rochelle) ; 2(6): 273-282, 2013 Jul.
Article in English | MEDLINE | ID: mdl-24527349

ABSTRACT

SIGNIFICANCE: The skin interfollicular epidermis (IFE) is an organism's first line of defense against a harmful environment and physical damage. During homeostasis and wound repair, the IFE is rejuvenated constantly by IFE stem cells (SCs) that are capable of both proliferation and differentiation. However, the identity and behavior of IFE SCs remain controversial. RECENT ADVANCES: Two opposing theories exist regarding homeostasis of the IFE. On the basis of morphological and proliferative characteristics, one posits that the IFE is composed of a discrete epidermal proliferative unit comprised of ∼10 transit-amplifying (TA) cells and a centrally located SC in the basal layer. The other suggests that homeostasis of the IFE is maintained by a single progenitor population in the basal layer. A recent study has challenged these two apparently distinct models and demonstrated that the basal layer of the IFE contains both SCs and TA cells, which make distinct contributions to tissue homeostasis and repair. Moreover, phosphorylation levels of the transcription factor p63, the master regulator of the proliferative potential of epidermal SCs, can be used to distinguish self-renewing SCs from TA cells with more limited proliferative potential. CRITICAL ISSUES: As technologies advance, IFE SCs can be identified at a single-cell level. Refinements of their identification and characterization are critical, not only for SC biology but also for the development of novel clinical applications. FUTURE DIRECTIONS: Understanding the signaling pathways that control self-renewal and differentiation of IFE SCs will aid in developing novel cell-based therapeutics targeting degenerative epidermal diseases and wound repair.

20.
Dev Dyn ; 242(2): 164-78, 2013 Feb.
Article in English | MEDLINE | ID: mdl-23172757

ABSTRACT

BACKGROUND: Although Xenopus laevis has been a model of choice for comparative and developmental studies of the immune system, little is known about organogenesis of the thymus, a primary lymphoid organ in vertebrates. Here we examined the expression of three transcription factors that have been functionally associated with pharyngeal gland development, gcm2, hoxa3, and foxn1, and evaluated the neural crest contribution to thymus development. RESULTS: In most species Hoxa3 is expressed in the third pharyngeal pouch endoderm where it directs thymus formation. In Xenopus, the thymus primordium is derived from the second pharyngeal pouch endoderm, which is hoxa3-negative, suggesting that a different mechanism regulates thymus formation in frogs. Unlike other species foxn1 is not detected in the epithelium of the pharyngeal pouch in Xenopus, rather, its expression is initiated as thymic epithelial cell starts to differentiate and express MHC class II molecules. Using transplantation experiments we show that while neural crest cells populate the thymus primordia, they are not required for the specification and initial development of this organ or for T-cell differentiation in frogs. CONCLUSIONS: These studies provide novel information on early thymus development in Xenopus, and highlight a number of features that distinguish Xenopus from other organisms.


Subject(s)
Gene Expression Regulation, Developmental/physiology , Neural Crest/embryology , Organogenesis/physiology , Thymus Gland/embryology , Transcription Factors/metabolism , Xenopus laevis/embryology , Animals , Base Sequence , DNA Primers/genetics , Forkhead Transcription Factors/genetics , Gene Expression Regulation, Developmental/genetics , Homeodomain Proteins/metabolism , Immunohistochemistry , In Situ Hybridization , Molecular Sequence Data , Reverse Transcriptase Polymerase Chain Reaction , Sequence Analysis, DNA , Sequence Homology , Species Specificity , Thymus Gland/anatomy & histology , Transcription Factors/genetics
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