The crooked neck dwarf lethal syndrome in the domestic fowl

Pun, C. F.

doi:10.1002/jez.1401260107

Cited by 11 publications

(1 citation statement)

References 38 publications

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“…It is only after E10 that mutant embryos exhibit the fusion of joints (ankylosis), including fused cervical vertebra that give rise to the abnormally short, crooked necks that are the basis for their name. Because the differentiation of muscles in the crooked neck dwarf have been described in detail at the light microscopic level in several previous studies (Asmundson, 1945;Pun, 1954;Harris, 1962;Elson, 1972;Wick and Allenspach, 1978;Kieny et al, 1983;Mauger et al, 1983); we have not attempted systematically to repeat those observations. However, we have confirmed these previous reports in observing that, prior to E8, muscle development appears similar in control and mutant embryos (Fig.…”

Section: Muscle Developmentmentioning

confidence: 67%

Neuromuscular development in the avian paralytic mutant crooked neck dwarf (cn/cn): further evidence for the role of neuromuscular activity in motoneuron survival

et al. 1997

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Neuromuscular transmission and muscle activity during early stages of embryonic development are known to influence the differentiation and survival of motoneurons and to affect interactions with their muscle targets. We have examined neuromuscular development in an avian genetic mutant, crooked neck dwarf (cn/cn), in which a major phenotype is the chronic absence of the spontaneous, neurally mediated movements (motility) that are characteristic of avian and other vertebrate embryos and fetuses. The primary genetic defect in cn/cn embryos responsible for the absence of motility appears to be the lack of excitation-contraction coupling. Although motility in mutant embryos is absent from the onset of activity on embryonic days (E) 3-4, muscle differentiation appears histologically normal up to about E8. After E8, however, previously separate muscles fuse or coalesce secondarily, and myotubes exhibit a progressive series of histological and ultrastructural degenerative changes, including disarrayed myofibrils, dilated sarcoplasmic vesicles, nuclear membrane blebbing, mitochondrial swelling, nuclear inclusions, and absence of junctional end feet. Mutant muscle cells do not develop beyond the myotube stage, and by E18-E20 most muscles have almost completely degenerated. Prior to their breakdown and degeneration, mutant muscles are innervated and synaptic contacts are established. In fact, quantitative analysis indicates that, prior to the onset of muscle degeneration, mutant muscles are hyperinnervated. There is increased branching of motoneuron axons and an increased number of synaptic contacts in the mutant muscle on E8. Naturally occurring cell death of limb-innervating motoneurons is also significantly reduced in cn/cn embryos. Mutant embryos have 30-40% more motoneurons in the brachial and lumbar spinal cord by the end of the normal period of cell death. Electrophysiological recordings (electromyographic and direct records form muscle nerves) failed to detect any differences in the activity of control vs. mutant embryos despite the absence of muscular contractile activity in the mutant embryos. The alpha-ryanodine receptor that is genetically abnormal in homozygote cn/cn embryos is not normally expressed in the spinal cord. Taken together, these data argue against the possibility that the mutant phenotype described here is caused by the perturbation of a central nervous system (CNS)-expressed alpha-ryanodine receptor. The hyperinnervation of skeletal muscle and the reduction of motoneuron death that are observed in cn/cn embryos also occur in genetically paralyzed mouse embryos and in pharmacologically paralyzed avian and rat embryos. Because a primary common feature in all three of these models is the absence of muscle activity, it seems likely that the peripheral excitation of muscle by motoneurons during normal development is a major factor in regulating retrograde muscle-derived (or muscle-associated) signals that control motoneuron differentiation and survival.

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Section: Muscle Developmentmentioning

confidence: 67%

Neuromuscular development in the avian paralytic mutant crooked neck dwarf (cn/cn): further evidence for the role of neuromuscular activity in motoneuron survival

et al. 1997

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Morphogenetic studies of the rabbit. XIII. The influence of the dwarf gene upon organ size and variability in race X

Latimer

Sawin

1955

Anat. Rec.

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Crooked neck dwarf in the Turkey

Asmundson

Pun

1956

J. Exp. Zool.

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NINE FIGURESI n 1949 several abnormal turkey (Meleagris gallopavo) embryos were found in a routine check of unpipped eggs laid by untrapnested F, hens from a cross of Black-winged bronze male with Palm females. Because of similarities to a lethal in the domestic fowl that had been called crooked neck dwarf (Asmundson, '45) the same name was given to this mutation.I n 1950 two male and four female descendants of the 1949 carrier birds produced some crooked necked progeny and other related males and females also produced lethal embryos. The following year ('51) crooked neck dwarf embryos were also obtained from an unselected strain of Broad Breasted Bronze (table 1).The ancestors of the crooked neck dwarf embryos came originally from five different turkey breeders and included birds of four plumage patterns. The nonbronze birds had all segregated out of Bronze stock within a pear or two of the time they were received from the breeders. Two of the strains were Broad Breasted Bronze and unrelated or only distantly related. The other three stocks were related, having all originated from a selected strain of Bronze. All three stocks had been crossed with Broad Breasted Bronze. It therefore seems probable that the Broad Breasted Bronze contributed the lethal gene. However the evidence does not exclude the possibility, (1) that the mutation occurred so long ago that it would be expected in both Broad Breasted and nonbroad breasted strains nor, (2) that the mutation has occurred independently among the ancestors of the birds found to be carriers of the gene in 1949 and 1951.

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The crooked neck dwarf lethal syndrome in the domestic fowl

Cited by 11 publications

References 38 publications

Neuromuscular development in the avian paralytic mutant crooked neck dwarf (cn/cn): further evidence for the role of neuromuscular activity in motoneuron survival

Neuromuscular development in the avian paralytic mutant crooked neck dwarf (cn/cn): further evidence for the role of neuromuscular activity in motoneuron survival

Morphogenetic studies of the rabbit. XIII. The influence of the dwarf gene upon organ size and variability in race X

Crooked neck dwarf in the Turkey

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