A Premature Stop Codon in RAF1 Is the Priority Candidate Causative Mutation of the Inherited Chicken Wingless-2 Developmental Syndrome.

The chicken wingless-2 (wg-2) mutation is inherited in an autosomal recessive fashion, and the resulting phenotype in mutant (wg-2/wg-2) individuals is a developmental syndrome characterized by absent wings, truncated legs, craniofacial as well as skin and feather defects, and kidney malformations. Mapping and genotyping established that the mutation resides within 227 kilobases (kb) of chromosome 12 in a wg-2 congenic inbred line. A capture array was designed to target and sequence the candidate region along with flanking DNA in 24 birds from the line. Many point mutations and insertions or deletions were identified, and analysis of the linked variants indicated a point mutation predicted to cause a premature stop codon in the RAF1 gene. Expression studies were conducted inclusive of all genes in the candidate region. Interestingly, RAF1 transcription was elevated, yet the protein was absent in the mutants relative to normal individuals. RAF1 encodes a protein integral to the Ras/Raf/MAPK signaling pathway controlling cellular proliferation, and notably, human RASopathies are developmental syndromes caused by germline mutations in genes of this pathway. Our work indicates RAF1 as the priority candidate causative gene for wg-2 and provides a new animal model to study an important signaling pathway implicated in limb development, as well as RASopathies.

A novel sex-linked mutant affecting tail formation in Hongshan chicken.

The Hongshan chicken is a Chinese indigenous breed that has two distinctly different tail types. Some chickens have stunted tails as compared to the normal phenotype, and they are termed rumpless. Rumplessness in other chicken breeds was caused by a reduction in the number of coccygeal vertebrae. However, X-ray examination showed that rumpless Hongshan chickens possess the normal number of coccygeal vertebrae. Our analyses of the main tail feathers and tissue sections led us to speculate that their stunted tail appearance may be the result of abnormal feather development. To investigate the genetic mechanism underlying rumplessness in Hongshan chickens, we analyzed the results of various crosses. The results indicated that rumplessness is a Z-linked dominant character. In addition, we chose some normal and rumpless individuals for pool-sequencing. Nucleotide diversity and Fst were calculated, and a selective sweep was detected on the Z chromosome. These analyses allowed us to reduce the search area to 71.8-72 Mb on the Z chromosome (galGal5.0). A pseudogene LOC431648 located in this region appeared a strong candidate involving in Wnt/ß-catenin signaling pathway to regulate feather development in chickens.

Pinching off syndrome in free-ranging white-tailed sea eagles (Haliaeetus albicilla) in Europe: frequency and geographic distribution of a generalized feather abnormality.

Generalized feather abnormalities are rarely documented in free-living birds. Pinching off syndrome (POS) is a feather abnormality in which all remiges and retrices become malformed and are lost during the nestling stage, rendering the bird unable to fly. To determine the frequency of occurrence and geographic distribution of this syndrome in white-tailed sea eagles (Haliaeetus albicilla) in Europe, we sent questionnaires to ornithologists in 19 countries within the European range of this species. We also searched for reported cases of sea eagles with feather abnormalities that met the criteria of POS. Overall, 32 nestlings or fledglings with POS were identified between 1975 and 2006. The geographic distribution of cases was primarily restricted to 4 European countries: Germany (17 cases), Poland (11 cases), the Czech Republic (3 cases), and Great Britain (1 case). Eleven eagles from Germany and 2 eagles from the Czech Republic were examined clinically. In 15 birds in which sex was determined, 8 were female and 7 were male. From 2000 to 2005, the 5-year incidence of POS in white-tailed sea eagles in Germany was 3.5 cases per 1000 birds. Although the etiology of this syndrome in wild sea eagles is unknown, our results support a possible genetic cause.

Elevated frequency of abnormalities in barn swallows from Chernobyl.

Ever since the Chernobyl accident in 1986, that contaminated vast areas in surrounding countries with radiation, abnormalities and birth defects have been reported in human populations. Recently, several studies suggested that the elevated frequency of such abnormalities can be attributed to poverty and stress in affected human populations. Here, we present long-term results for a free-living population of barn swallows, Hirundo rustica, demonstrating the presence of 11 morphological abnormalities in populations around Chernobyl, but much less frequently in an uncontaminated Ukrainian control population and three more distant control populations. The presence of these abnormalities in barn swallows is associated with reduced viability. These findings demonstrate a link between morphological abnormalities and radiation in an animal population that cannot be attributed to poverty and stress. The most parsimonious hypothesis for abnormalities in animal and human populations alike is that the effects are caused by the same underlying cause, viz. radiation derived from the Chernobyl accident.

Morbidity of free-ranging white-tailed sea eagles (Haliaeetus albicilla) in Germany.

Between September 1998 and December 2006, 87 injured or sick free-ranging white-tailed sea eagles (Haliaeetus albicilla) from Germany were admitted to the Small Animal Clinic, Free University of Berlin. Most birds were adults (43%) followed by nestlings/fledglings (26%), immature birds (18%), and juveniles (13%). In all age groups more females than males were presented. Birds with trauma-associated injuries were most often admitted, followed by lead toxicosis and feather anomalies in fledglings. Collision with anthropogenic structures was the most common cause of injuries in all age classes. Lesions caused by intraspecific aggressions were mainly found in adults, whereas a generalized feather abnormality (pinching off syndrome) was diagnosed only in fledglings. Of all birds, 25% were released back to the wild, 21% died, and 54% were not releasable or were euthanatized.

Sonic Hedgehog functions by localizing the region of proliferation in early developing feather buds.

Feathers are formed following a series of reciprocal signals between the epithelium and the mesenchyme. Initially, the formation of a dense dermis leads to the induction of a placode in the overlying ectoderm. The ectoderm subsequently signals back to the dermis to promote cell division. Sonic Hedgehog (Shh) is a secreted protein expressed in the ectoderm that has previously been implicated in mitogenic and morphogenetic processes throughout feather bud development. We therefore interfered with Shh signaling during early feather bud development and observed a dramatic change in feather form and prominence. Surprisingly, outgrowth did occur and was manifest as irregular, fused, and ectopic feather domains at both molecular and morphological levels. Experiments with Di-I and BrdU indicated that this effect was at least in part caused by the dispersal of previously aggregated proliferating dermal cells. We propose that Shh maintains bud development by localizing the dermal feather progenitors.

Adaptive allocation of stress-induced deformities on bird feathers.

Physiological stress during ontogeny is known to cause abnormalities in keratin structures of vertebrates, but little is known about if and how organisms have evolved mechanisms to reduce the negative effects of these abnormalities. Stress experienced during avian feather growth is known to lead to the formation of fault bars, and thereby to the weakening of feathers because of shortage and slimming of barbules. Here we propose and test a new hypothesis (the 'fault bar allocation hypothesis') according to which birds should have evolved adaptive strategies to counteract this evolutionary pressure. In particular, we predicted and tested the idea that in flying birds, natural selection should have selected for mechanisms to reduce fault bar load on feathers with high strength requirements during flight. Data on the growth of feathers of nestling white storks (Ciconia ciconia) revealed a consistent allocation of more, and more intense, fault bars in innermost than in outermost wing feathers as predicted by our hypothesis. Moreover, the same pattern emerged from feathers of adult storks. We discuss the generality of our results, and suggest avenues for further investigations in this area.

BMPs induce dermal markers and ectopic feather tracts.

Bone morphogenetic protein (BMP) signaling is known to be involved in multiple inductive events during embryogenesis including the development of amniote skin. Here, we demonstrate that early application of BMP-2 to the lateral trunk of chick embryos induces the formation of dense dermis, which is competent to participate in feather development. We show that BMPs induce the dermis markers Msx-1 and cDermo-1 and lead to dermal proliferation, to expression of beta-catenin, and eventually to the formation of ectopic feather tracts in originally featherless regions of chick skin. Moreover, we present a detailed analysis of cDermo-1 expression during early feather development. The data implicate that cDermo-1 is located downstream of BMP in a signaling pathway that leads to condensation of dermal cells. The roles of BMP and cDermo-1 during development of dermis and feather primordia are discussed.

[Breed-dependent anomalies in ornamental birds]. / Zuchtbedingte Anomalien bei Ziervögeln.

Following a definition of the terms pet bird and domestication, and a description of important mechanisms which may have played a role during domestication, a short review is given on the various changes that occurred and have been used selectively by humans: changes in body size, skin and feathers, skull, metabolisms, and the central nervous system including behavior and disturbances of behavior. Implications for animal welfare are considered.

Assessing the effects of the naked neck gene on chronic heat stress resistance in two genetic populations.

The effect of the naked neck (Na) gene on resistance to chronic heat stress was studied in the F2 generation of two populations of chickens genetically differing in growth. The Na gene was introduced into the Athens-Canadian randombred (ACRB), a small BW population, and into a large BW commercial broiler population. Naked neck and normally feathered birds were maintained in either a chronic heat stress (32 C) environment or a control (21 C) environment from 4 to 8 wk of age. Body weight, BW gain, feed consumption, and feed efficiency were calculated at 4, 6, and 8 wk. The 32 C environment significantly reduced gain and feed consumption at all age intervals in both populations. Feed conversion ratio (FCR) was lower in the 32 C environment in the ACRB population, but in the broiler population FCR either was the same or increased when compared with the 21 C environment. In the F2 generation of both populations the naked neck birds were significantly larger than the normally feathered birds although the two types segregated from the same parents. In the ACRB population the relative growth response was not significantly different between naked neck and normal feathered birds, indicating that the Na gene did not confer resistance to chronic heat stress in the small BW population. In the broiler population, an assessment of the relative growth response in the 32 C environment showed that the naked neck birds had a smaller reduction in BW gain and better feed efficiency than the normally feathered birds, indicating that in the large BW broiler population the Na gene did confer resistance to chronic heat stress.

Defective Down syndrome in chicks is not caused by riboflavin deficiency in breeders.

1. Riboflavin-deficient practical and semi-purified diets were fed to broiler breeder hens. 2. Yolk and albumen riboflavin concentrations were depressed by the deficient diets and cases of curled toes were seen in the chicks. 3. The few instances of defective down did not resemble cases seen in field outbreaks of a condition involving depressed hatchability and a defective down syndrome. 4. It is concluded from observations in this experiment and in the field outbreaks that there is a condition in breeding chickens causing depressed hatchability and defective down that is not attributable to riboflavin deficiency.

Valine deficiency. 2. The effect of feeding a valine-deficient diet during the starter period on performance and leg abnormality of male broiler chicks.

Using force-feeding and pair-feeding techniques, two experiments were conducted to investigate the problem of leg abnormality associated with feeding a Val-deficient diet as compared with a diet deficient in all the branched chain amino acids (BCAA) or a Val-supplemented diet. The BCAA-deficient diet contained .96, .52, and .63% of Leu, Ile, and Val, respectively. The Val-deficient diet contained 1.37 Leu, .82 Ile, and .63% Val. The Val-supplemented diet contained 1.37 Leu, .82 Ile, and .83% Val. In both studies birds fed the Val-supplemented gained more weight than birds in the other two groups. Although birds on Val-deficient and BCAA-deficient diets had similar weight gain, the former were lethargic and showed feather and leg abnormalities. Bone ash and bone calcium for Val-deficient birds were the lowest among the three groups studied (P < .05). The levels of the BCAA in plasma reflected those of the treatment diets. Plasma hydroxyproline was lowest in birds fed the Val-deficient diet (P < .05), indicating a reduction in bone collagen breakdown. Kidney function measurements were the same for birds on the Val-supplemented and Val-deficient diets. Fractional excretion of calcium in Val-deficient birds (.13%), however, was three times higher than that of Val-supplemented birds (P < .05). The results indicated that Val deficiency per se increased calcium excretion in urine and induced leg abnormality in young chickens.

[Skin and plumage changes in domestic birds. II. Plumage changes]. / Haut- und Gefiederveränderungen bei domestizierten Vögeln. Teil II: Gefiederveränderungen--2.

The study describes plumage modifications and specific feather malformations, as related to the domestication process of different poultry species. The modifications include naked necks, leg feathering, frizzle feathering, silky feathering, fat quills, and feather abnormalities caused by behavioural hypertrophies. Most of these plumage modifications correspond to the breed standard for exhibition poultry fancy. However, they impair the normal function of these animals. The negative influences comprise disorders in social behaviour, loss of typical plumage functions and disabilities of normal mobility, as well as genetic defects and pathogenic predispositions.

Abnormal feathering of chicks caused by scirpenol mycotoxins differing in degree of acetylation.

Graded levels of the Fusarium mycotoxins, scirpentriol (STO), 15-monoacetoxyscirpenol (15-MAS), 4,15-diacetoxyscirpenol (4,15-DAS), and 3,4,15-triacetoxyscirpenol (TAS), were fed to chicks until 3 wk of age. The primary wing feathers, which were scored visually on a scale of 1 to 5 using a newly created scoring scheme, were altered in a dose-related fashion by 15-MAS [minimum effective dose (MED) = .5 microgram/g diet], 4,15-DAS (MED = 2 micrograms/g), and STO (MED = 4 micrograms/g) but not by TAS (MED greater than 8 micrograms/g). The minimum growth inhibitory doses were 2 micrograms/g for STO, 15-MAS, and 4,15-DAS and 8 micrograms/g for TAS. The main alteration of the feathers was a frayed and missing web on the medial side of the distal half of the feather. The shafts of the feathers tended to have an accentuated medial curve. These results imply that the feather alterations associated with corn and feed infested with Fusarium spp. might be caused by trichothecene mycotoxins such as the scirpenols.

[Skin and plumage changes in domestic birds. II. Plumage changes--1]. / Haut- und Gefiederveränderungen bei domestizierten Vögeln. Teil II: Gefiederveränderungen--1.

Modifications of the plumage and specific feather malformations, as developed during the domestication process of different poultry species are described. The modifications include henny feathering, elongated feathers, ear tufts, muffs, and increased numbers of tail feathers. The greater part of these plumage modifications is generally of interest for exhibition poultry fancy. Several of the plumage abnormalities presented distinctly impair the normal species-typical way of life of the animals concerned. The spectrum of negative influences comprises disorders in social behaviour, loss of, or restrictions in typical plumage functions such as weather susceptibility, as well as disabilities of normal mobility. Finally, genetic defects and pathogenic predispositions are also connected with such plumage modifications.