Quail–Chick Chimeras and the Avian Neural Crest
Cells of the japanese flinch, Coturnix coturnix japonica, hold nucleus with boastfully accumulations of heterochromatin that can be distinguished from the nucleus in cells of the common bird, Gallus domesticus, in which heterochromatin is dispersed uniformly ( illustrated in Figure 15.4 ). Grafting cells or tissues from japanese quail to chick therefore provides a permanent wave marker with which to assess development of the graft cells. such embryo frequently are referred to as quail–chick chimeras, although the whole embryo is not chimera, and often not even a unmarried weave is chimeric as when host cells are fully replaced with transplant cells as happen when an integral region of neural crown is transplanted. regulation is ( normally ) not an publish unless only one side of the neural crest is transplanted, in which character cells can migrate across from the host crest. Quail–chick chimeras were beginning used by Amprino et alabama. ( 1968 ) in an psychoanalysis of limb-bud exploitation. Quail–chick chimera to investigate the nervous cap and NCCs have been most elegantly and productively used by Nicole Le Douarin and her group in Nogent-sur-Mer in Franc and by Drew Noden at Cornell University in Ithaca, NY15. By transplanting 3H-thymidine-labelled and/or quail neural crest into chick embryo in a decade-long serial of studies Noden ( 1998 ) demonstrated that
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- NCCs from each cranial area have a specific pattern of migration that is not irreversibly fixed before migration begins – regions can be exchanged and the migrant patterns remain normal ; and that
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- the bones of the skull develop from mesencephalic ( midbrain level ) and hindbrain nervous crest ( recall that mapping the origins of the bones of amphibian skulls is a lot more refractory to analysis ).
furthermore, Noden ’ south studies uncovered some of the environmental interactions that direct the migration of cranial neural peak cells, the neural-crest origin of periocular mesenchyme, and similarities in the ability of periocular and visceral arch environments to promote chondrogenesis. His studies revealed early specification of patterns of cell migration and that the broad radiation pattern of the craniofacial skeleton is established before NCCs begin to migrate. First, arch crest transplanted to second or third base arch positions in the nervous pipe migrates to the hyoid arch but produces mandibular ( inaugural arch ) skeletal structures, including an ectopic beak ( Box 17.1 ) and, amazingly, elicits mandibular arch muscles from what should have formed hyoid arch muscles. The muscles are not of neural-crest lineage ( Noden, 1986 ) but their connection tissue sheaths are, as demonstrated for dame by Köntges and Lumsden ( 1996 ) and for the Oriental fire-bellied frog, Bombina orientalis, by Olsson et alabama. ( 2001a ). Box 17.1 Bird Beaks The epithelium of the frontonasal serve in dame embryo contains a boundary region marked by Shh/Fgf8 expression on either side. This region specifies the dorsoventral axis of the upper beak, and elicits ectopic upper and lower beaks when transplanted into other sites within craniofacial mesenchyme. We know that the source of that mesenchyme is the neural crest. The species specificity of beak form ( Figure 17.4 and see besides Figure 7.7 ) is confront in NCCs. Transplanting NCCs from japanese quail into duck embryo produces quail beaks and vice versa. The transplant NCCs initiate patterns of gene expression typical of the donor and modifying patterns of expression of genes such as Shh and Pax6 in server tissues to conform to the patterns typical of the donor tissues. The character of Bmp4 in beak shape and size is discussed in chapter 44a. Beaks form in response to epithelial–mesenchymal interaction ( second ). histological studies on dame beak by Kingsbury et aluminum. ( 1953 ) documented a deepening of the epidermis adjacent to proliferating mesenchyme at 3 days of brooding, evocative of that described in the lower jaw by Jacobson and Fell ( 1941 ) and discussed in Chapters 18 and 19Chapter 18Chapter 19. The edges of the beaks of ducks are raised into ridges, frequently referred to as ‘ tooth ridges ’ although all birds lack teeth. Hayashi ( 1965 ) used a series of tissue recombinations between duck ( Figure 17.4 ) and dame – a mouse–chick recombination is shown in Figure 17.5 – to demonstrate interaction during beak development and ectomesenchymal operate of epithelial differentiation. Duck oral mesenchyme combined with dame oral epithelium produces a duck beak complete with tooth ridge ; while chick oral mesenchyme combined with duck oral epithelium produces a chick peck lacking a tooth ridge. Tonegawa ( 1973 ) conducted a exchangeable series of weave recombinations using beak and early skin derivatives to demonstrate that ‘ beak ’ epithelium from 6-day-old embryo would not form a beak unless combined with mesenchyme, and that the inductive ability of beak mesenchyme persists beyond think up. Studies on the chick mutant cleft primary coil palate ( cpp ), in which the upper peck is shortened but the lower beak is normal – a phenotype exchangeable to that seen in paralytic embryo – show that the growth defect resides in the epithelial cover of the frontonasal process. Fgf8 is not down-regulated and so remains active in the frontonasal epithelium in mutant embryo for at least 2 days after it is down-regulated in wild-type embryo. Increased levels of cell death in upper beaks besides occur at later stages of development in mutant embryo. Cell death in the lower beak is normalb. Noden demonstrated that proboscis myotome grafted into cranial mesenchyme adjacent to the neural tube produces ectopic cartilages and ectopic membrane bones, and, surprisingly, that the ectopic cartilages – which are mesoblastic in origin – fail to fuse with host neural crest–derived cartilage, a find oneself that relates to the likely for interaction between ( replacement of ) neural crest– and mesodermally derived mesenchyme, discussed earlier in this chapter, and demonstrated experimentally by Fyfe and Hall ( 1979 ). last, Noden analysed the implications of developmental processes affecting NCCs for the development of craniofacial morphology16. Within dame heads, only the occipital bones and bones of the otic capsule are wholly of mesoblastic origin. early bones, such as the facade, are formed from mesoblastic and ectomesenchymal cells ( Couly et al., 1993, 1998Couly et al., 1993Couly et al., 1998 ). I could devote a solid chapter to an psychoanalysis of studies on the nervous crest or mesoblastic origin of the craniofacial skeletal system of the domestic chicken. alternatively, I refer you to Hall ( *2009 ) for a discussion of the many issues involved. A complete number of all the skull bones and cartilages derived from nervous crest cells, compiled from studies undertaken in four laboratories between 1974 and 1996, is provided by Gross and Hanken ( 2008 ) as their mesa 2. The ability/role of the nervous crest to form cranial bony elements in chick embryo – the skeletogenic neural crest – extends from the mid-prosencephalon caudally to the level of the one-fifth pair of somites, a area known as the cranial neural peak ( Figures 17.1, 17.3 and 17.6 ). Cartilages of neural-crest origin in more caudally locations do exist – secondary cartilage on clavicles, discussed in chapter 1617, and cardiac cartilages ( Box 17.2 ) – but these cartilages ( and the bone of the clavicle ) rise from cranial neural crest cells that migrate caudally. Trunk neural crest, which is defined as peak caudal to somite five ( Figures 17.1 and 17.6 ) does not form cartilage ( but see below ) or bone .
figure 17.6. Fate maps of the formation of cartilage, teeth and median-fin mesenchyme from cranial and/or trunk neural crown ( CNC, TNC ) from the Mexican axolotl, Ambystoma mexicanum. The maps are dorsal views of neurula-stage embryo ( anterior to the clear ). The nervous folds dwell along the center of each neurula. A horizontal line denotes the traditional boundary of cranial and torso nervous crest ( as based on chondrogenic ability of NCCs ; see text for details ). On the leave of each neurula is the destine function ( Fate ) as expressed during normal development. On the right is the potential ( Potential ) to form the three tissues after neural crest from each grade was isolated and cultured with pharyngeal endoderm. ( A ) Potential to form cartilage ( C ) coincides with the area from which cartilage normally forms ( Fate ), confirming the traditional boundary between CNC and TNC for chondrogenesis. ( B ) Teeth ( O, odontogenic neural crown ) normally form from a more restrict region of the CNC ( shown on the entrust ). As illustrate in Figure 18.4, teeth can form from a more extensive region that extends back tooth to the normally recognised CNC/TNC boundary as based on chondrogenesis. ( C ) Dorsal-fin mesenchyme ( F ) normally forms from TNC ( left ) but can form from NCCs at any charge ( right ). See text and Graveson et aluminum. ( 1997 ) for details . Box 17.2 Cardiac and Ectopic Cartilages and Bones Cartilages and bones in the heart may seem an unlikely inclusion in a chapter devoted to the neural crest origin of bony tissues. Where they have been investigated, and not many have been, these elements arise from neural crest–derived mesenchyme, as do the valves and septum of the heart. indeed well recognised is this contribution from the nervous crest that we refer to the most caudal area of the cranial peak, the region from which NCCs emigrate to seed the developing kernel, as the cardiac neural crest ( Olson and Hall, 2000 ; Hutson and Kirby, 2003 ; Hall, *2009 ) .
Constitutive Cardiac Cartilages
Bones and/or cartilages are amazingly common elements of vertebrate hearts. equally far as I can tell, these are normal, non-pathological, and not associated with contagion, parasites or injury. indeed, in some species, all individuals have a cardiac cartilage. In such taxonomic group, cardiac cartilage is a convention chemical element of the endoskeleton, neither a sesamoid bone nor ectopic .
Distribution and Development
To my cognition, bony elements have been reported in the hearts of four of the five classes of vertebrates, amphibians being the one exception. That said, cardiac bony elements have been reported only occasionally in fish, specifically in the wall of the bulbus arteriosus in eight specimens from four species of teleost fish fishesa.
cardiac cartilage in reptiles – in turtles, alligators, crocodiles and 11 of 42 species of snakes studied, but not in the three species of lizards examined – shows no obvious correlation with size, taxonomic group or habitat. Although there are reports of cardiac cartilage in rodents, cattle and rabbits, its frequency in mammals is abject : 33 cases/1,000 rats, 15 cases/1000 mouse. Ossified cartilages arrant with marrow and located in the aortal gang are more park in rabbits, a group that besides has an perplex proclivity to form bony tissue ectopicallyb. cartilage is a constituent have of the proximal aorta, pneumonic luggage compartment and crescent valves of dame embryo from H.H. 37 ( 11 days of incubation ) forth. The neural-crest origin of these cardiac cartilages has been demonstrated in chick and quailc. At the very least, such cartilage expands the number of nervous crest–derived cartilages and demonstrates that cranial ( cardiac ) crest can contribute skeletal elements to the luggage compartment. Some of our best understand of cardiac cartilage development comes from a developmental study of a turtle, the spanish terrapin, Mauremys leprosa ( D. López et al., 2003 ). The major constituent cartilage arises from a mesenchymal condensation ( Chapter 19 ) that extends along the aorticopulmonary septum and the primordium of the pars fibrosa of the ventricular horizontal septum. The initial condensation expresses neither smooth muscle [ alpha ] -actin nor character II collagen. Type II collagen is deposited and chondrogenesis begins in the center of the compression, spreading peripherally to form a hyaline cartilage that extends along the proximal part of the aorticopulmonary septum and the pars fibrosa of the horizontal septum. This cartilage lacks a perichondrium or any gestural of chondrocyte hypertrophy, mineralisation or ossification. A second hyaline cartilage, which arises between three and 18 months after give birth, extends along the fistula wall of the right crescent valve of the correct aorta to penetrate the fibrous shock absorber that supports a fortune of the valve. Forty of 351 ( 11.4 % ) of the pneumonic valves of Syrian ( golden ) hamsters, Mesocricetus auratus, have cartilage along the fibrous attachment of the valves ( Figure 17.7 ), while 25 % have cartilage in the cardinal fibrous area of the affection. Type II collagen is a typical feature of these cartilages. The percentage may be excessively broken to regard these as constituent, although the heart cartilages are present from soon after parentage and therefore are not a consequence of heart degeneracy or aging – making hamsters an interest species in which to investigate the conditions under which cardiac cartilages arise. López and colleagues maintained that not all these cartilages are mechanically induce, and discuss their potential neural crest cell origind. A far report of cartilages in heart valves in syrian hamsters provides a model system for analysis of the development of such cartilages in answer to mechanical stimulation. One inbred family of syrian hamsters has a high incidence of bicuspid aortal valves. Sixty per penny of these valves develop cartilages, two-thirds by the one-sixth week of life. many of these cartilages mineralize. Sans-Coma et alabama. ( 2005 ) attribute the universe of these cartilages and their mineralization to the ‘ acute mechanical foreplay ’ at these sites, the calcify cartilages acting to resist damage to the valves .
Ectopic Cardiac Cartilages and Bones
skeletal elements besides form ectopically in the hearts of diverse mammals in response to a variety of abnormal circumstances or interventions. Some of these ectopic elements have been shown to be NCC in origin. Ectopic cartilages or bone are associated with : ( one ) congenital heart abnormalities in humans ; ( two ) develop in cardiac valves implanted into sheep ( cartilage in 12/120 implants in station for longer than 13 weeks, one with bone ) ; ( three ) break after heart–lung and double lung transplants in humans, in about all of whom mineralisation or ossification occurs ( some of this cartilage may have arisen from bronchial cartilages ; see below ) ; ( intravenous feeding ) develop in dogs given kernel prostheses in which 11/15 formed cartilage and 5/15 cram ; ( vanadium ) and develop in rats given auxiliary kernel graft ( both cartilage and bone form from connection tissue cells of the endocardium of the graft ) east. Carrageenan, a polysaccharide produced by loss alga, consists of alternating 3-linked-ß-d-galactopyranose and 4-linked-α-d-galactopyranose units. cartilage can be induced in the walls of wimp aorta by injecting carrageenin, which presumably acts as a polysaccharide precursor. intravenous injection of papain into rabbits besides induces aortal cartilage, which is replaced by bone with kernel ( McCandless et al., 1963 ; Tsaltas, 1962 ). Ectopic pneumonic cartilage and bone happen in newly hatched chicks. The given is that misplace mesenchymal cells or chondrogenic precursors produced these ectopic bony tissues ( Figure 17.8 ) f. Cartilages ( or bones ) that form in the lungs, on the other hand, are improbable to be nervous crest in origin because NCCs make no contribution to the lungs. Tsukioka et alabama. ( 2012 ) attributed the ectopic bone in the bronchus of a individual male as metaplastic bone, bacterial infections having been proposed previously as a stimulation to bone formation. Irradiating guinea pig bed lungs results in geological formation of lamellar bone with hematopoietic tissue ( Figure 17.9 ; Knowles, 1984 ) .
Shared Molecular Pathways
Heart valves are a building complex connective weave with distinct fibrosa, spongiosa and elastin-rich layers ; abnormal remodelling of heart valves is a common change associated with heart valve disease. possibly amazingly – it was surprising to me – heart valves, cartilage, tendon and bone partake gene regulative pathways whose primary routine is in the remodelling of the different ECMs. At least three shared pathways are known :
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- Fgf4→Scleraxis→Tenascin regulates ECM geological formation in valves and tendons .
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- RankL→NfaTc1→Cathepsin K are activated at the tips of remodelling valves and in osteoclasts .
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- Bmp2→Sox9→Aggrecan regulates valve exploitation and initiation of chondrogenesis ( Lincoln et al., 2006 ) .
additionally, construction of multiple Wnt genes, Wnt ligands, receptors and modifying proteins in shiner and wimp embryo, and the association of Wnt signalling with osteogenesis ( discussed in respective chapters ), led Alfieri et aluminum. ( 2010 ) to look for formulation of bony genes during affection valve development. Periostin, osteonectin and Id2 are expressed in the collagenous fibrosa layer of the valves of chick embryo at 14 days brooding. Valve cells cultured in an osteogenesis-promoting medium read enhanced expression of these genes and imprint nodules of bone. summation of Wnt3a enhanced expression of periostin and osteocalcin, both markers of early osteogenesis, but did not induce genes associated with belated phases of osteogenesis. consequently, although cells of chick kernel valves have the potential for osteogenesis, signals for overt osteogenesis normally are not confront in vivo.
about no information is available on NCCs, their migration or their contribution to the skeleton in species of birds early than the domestic wimp, although chimeras have been generated between dame and duck and japanese quail ; see Schneider and Helms ( 2003 ), A. S. Tucker and Lumsden ( 2004 ) and Solem et aluminum. ( 2011 ) for some studies. Because of sake in a muscle, the pseudomasseter, found only in parrots, Tokita ( 2006 ) examined NCC migration in the australian cockateel, Nymphicus hollandicus. The only difference when compared with chick was earlier migration of NCCs into the foremost intuitive arch in the cockateel. Parrots have two novel structures associated with beak function, one skeletal, one mesomorphic. Tokita et aluminum. ( 2007 ) documented that the two states of the morphology of the suborbital region of the skull in parrots ( lacking or in respective degrees of presence ) correlate with two states of the pseudomasseter muscleman ( well-developed or under-developed ) and with clock of embryonic specialization of the pseudomasseter muscle ( early and late ). Whether changes in nervous crest cell migration/differentiation besides are associated with this change in the clock of muscle development remains for future studies .
