Mutations in Frizzled 6 cause isolated autosomal-recessive nail dysplasia

Inherited and isolated nail malformations are rare and heterogeneous conditions. We identified two consanguineous pedigrees in which some family members were affected by isolated nail dysplasia that suggested an autosomal-recessive inheritance pattern and was characterized by claw-shaped nails, onychauxis, and onycholysis. Genome-wide SNP array analysis of affected individuals from both families showed an overlapping and homozygous region of 800 kb on the long arm of chromosome 8. The candidate region spans eight genes, and DNA sequence analysis revealed homozygous nonsense and missense mutations in FZD(6), the gene encoding Frizzled 6. FZD(6) belongs to a family of highly conserved membrane-bound WNT receptors involved in developmental processes and differentiation through several signaling pathways. We expressed the FZD(6) missense mutation and observed a quantitative shift in subcellular distribution from the plasma membrane to the lysosomes, where the receptor is inaccessible for signaling and presumably degraded. Analysis of human fibroblasts homozygous for the nonsense mutation showed an aberrant response to both WNT-3A and WNT-5A stimulation; this response was consistent with an effect on both canonical and noncanonical WNT-FZD signaling. A detailed analysis of the Fzd(6)(-/-) mice, previously shown to have an altered hair pattern, showed malformed claws predominantly of the hind limbs. Furthermore, a transient Fdz6 mRNA expression was observed in the epidermis of the digital tips at embryonic day 16.5 during early claw morphogenesis. Thus, our combined results show that FZD6 mutations can result in severe defects in nail and claw formation through reduced or abolished membranous FZD(6) levels and several nonfunctional WNT-FZD pathways.

Comparison of Stress Zones in Finite Element Models of Deformed Bovine Claw Capsules

Pathological claw formations occur subsequent to irregular or prolonged claw trimming periods and as a result of improper flooring. Clinical experience and material testing finds horn of minor quality to be associated with the malformations. Finite element models (FEM) of a flat claw (FC), a contracted claw (CC), and a laminitic claw (LC) were designed from native claw specimens to combine material properties and altered claw geometry for stress analysis. The FEM were created by digitizing the typically deformed exungulated claw capsule by means of computed tomography or digital photography. The derived geometry data were meshed with finite elements and the material properties were attributed. Loading was performed via vertical load vectors according to the suspensory and support apparatus of the bovine digit. All FEM were loaded on soft floors. Loading of the FEM of the FC with 756 N exhibited maximum stress values of 3.32 MPa in the dorsal wall, that of the CC exhibited comparably lower stress of 1.33 MPa in the distal abaxial wall, and the model of the LC showed maximum stress of 4.51 MPa in the region of the dorsal border, all at the same loading. The solar surfaces and the corresponding imprints showed stress concentrations in the palmar aspect of the bulb in the FC, a highly stressed bearing margin of the abaxial wall in the CC, and a diffusely stressed sole and bulb in the LC in contrast to the sound claw models. The FEM of the selected pathological claw forms (FC, CC, LC) calculated high stress zones exactly at locations in the claw wall and sole where clinical experts expect the typical claw lesions for these pathologies. These results were obtained simply by exchanging the outer form of the claw capsules; the method of loading and type of flooring for these pathological models were equivalent to those of the sound FEM. It is highly possible that the stress zones derived from these calculations represent corium compression in reality, and these data support the pathophysiological theory that claw lesions may arise as a consequence thereof.

Cell autonomy of the mouse claw paw mutation

Mice homozygous for the autosomal recessive mutation claw paw (clp) are characterized by limb posture abnormalities and congenital hypomyelination, with delayed onset of myelination of the peripheral nervous system but not the central nervous system. Although this combination of limb and peripheral nerve abnormalities in clp/clp mice might suggest a common neurogenic origin of the syndrome, it is not clear whether the clp gene acts primarily in the neurone, the Schwann cell or both. In the work described here, we address this question of cell autonomy of the clp mutation through reciprocal nerve grafting experiments between wild-type and clp/clp animals. Our results demonstrate that the clp mutation affects the Schwann cell compartment and possibly also the neuronal compartment. These data suggest that the clp gene product is expressed in Schwann cells as well as neurones and is likely to be involved in direct axon--Schwann cell interactions. Within the Schwann cell, clp affects a myelin-related signaling pathway that regulates periaxin and Krox-20 expression, but not Oct-6.

Injection of corticosteroids, hyaluronate, and amikacin into the navicular bursa in horses with signs of navicular area pain unresponsive to other treatments: 25 cases (1999-2002)

OBJECTIVE

To determine history, clinical and radiographic abnormalities, and outcome in horses with signs of navicular area pain unresponsive to corrective shoeing and systemic nonsteroidal anti-inflammatory drug administration that were treated with an injection of corticosteroids, sodium hyaluronate, and amikacin into the navicular bursa.

DESIGN

Retrospective study.

ANIMALS

25 horses.

PROCEDURE

Data collected from the medical records included signalment, history, horse use, severity and duration of lameness, shoeing regimen, results of diagnostic anesthesia, radiographic abnormalities, and outcome.

RESULTS

17 horses had bilateral forelimb lameness, 7 had unilateral forelimb lameness, and 1 had unilateral hind limb lameness. Mean duration of lameness was 9.2 months. All horses had been treated with corrective shoeing and nonsteroidal anti-inflammatory drugs for at least 6 months; 18 had previously been treated by injection of corticosteroids and sodium hyaluronate into the distal interphalangeal joint. Fourteen horses had mismatched front feet, and 21 horses had signs of pain in response to application of pressure over the central aspect of the frog. Palmar digital nerve anesthesia resulted in substantial improvement in or resolution of the lameness in all horses. Twenty horses (80%) were sound and returned to intended activities 2 weeks after navicular bursa treatment; mean duration of soundness was 4.6 months. Two horses that received numerous navicular bursa injections had a rupture of the deep digital flexor tendon at the level of the pastern region.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that navicular bursa treatment may provide temporary improvement in horses with signs of chronic navicular area pain that fail to respond to other treatments.

[Case report--polydactyly in a German holstein calf]

A female German Holstein twin calf showed polydactyly in both front limbs and in one of the hind limbs. In three limbs an additional medial toe was seen. No malformations of the limbs were present in the male twin partner and four maternal half sibs. The analysis of the pedigree revealed that the affected calf had common ancestors. The coefficient of inbreeding of the affected calf was 1.312%. As a monogenic or digenic inheritance was suspected in similar cases, it may be probable that the polydactyly observed here has a genetic background.

Sand cracks, horizontal fissures, and other conditions affecting the wall of the bovine claw

The wall of the bovine claw is created only by the dermis beneath the coronary band. Keratogenic tissues in this region are susceptible to nutritional changes or stress, which changes the characteristics of the horn produced. Horizontal grooves or fissures result that weaken the claw wall and are instrumental in generating many vertical fissures. The rate at which the claw grows can be used to calculate the date of a nutritional insult.

Abnormalities of hoof growth and development

The normal development of the horn capsule (epidermis), with its dermal support (corium), is described. Abnormalities of horn growth may be caused by changes in blood flow (laminitis), the biomechanics of weight bearing, heritable developmental conditions, and other changes of unknown cause.

Hoof horn abnormalities in Lipizzaner horses and the effect of dietary biotin on macroscopic aspects of hoof horn quality

This study involved a macroscopic evaluation of hoof quality in 152 Lipizzaner horses (130 from Austria and 22 from other countries) and a controlled double blind trial of the effects of biotin on hoof horn growth and quality over 19 months in 42 stallions from the Spanish Riding School (SRS) in Vienna. Using a grading system that incorporated evaluation of horn wall, white line, sole and frog, the macroscopic study revealed the following: 90% of the Austrian Lipizzaners had soft white lines and crumbling, fissured horn at the bearing border of the walls; 39% of the stallions of the SRS, > 4-years-old, had medium to severe hoof horn changes. Daily administration of 20 mg biotin to a test group of horses (n = 26) and a placebo to a control group (n = 16) showed that after 9 months the test group had significantly improved compared to the beginning of the trial and the placebo group (P < 0.01). In the test group, further improvement was observed during the following 5 months and, subsequently, the same good level of hoof condition was maintained over 3 further years of observation. Growth rate of the horn wall was equal in the biotin and placebo group, being 7 mm/28 days, giving a wall renewal period of 11 months. Mean plasma biotin level of untreated horses was 350 ng/l; plasma levels of biotin supplemented horses were > 1000 ng/l. It was concluded that continuous dietary supplementation with biotin at a daily dose of 20 mg is indicated to improve and maintain hoof horn quality in horses with less than optimum quality hoof.

Surgical management of syndactyly in a dog

This report describes the treatment of simple syndactyly in a Golden Retriever. The left forepaw lacked cutaneous separation between the digits and had confluent metacarpal and digital pads. After vigorous exercise, the dog had intermittent non-weight-bearing lameness involving the affected forepaw. The lameness may have resulted from stretching of the thin skin on the dorsum of the paw as the digits attempted to spread during weight bearing. Surgical separation of digits 3 and 4 was performed by creating an interdigital web space with dorsal and palmar skin flaps and by covering the exposed axial surfaces with full-thickness skin grafts. At 11 weeks after surgery, the lameness had improved and the dog's level of activity had increased.

Bilateral hind limb hypoplasia in a foal

Hypoplasia affecting both hind limbs was observed in a neonatal foal. Scintigraphy aided in establishing diagnosis and prognosis. Radiography revealed an abnormally shaped middle phalanx and lack of the distal phalanx and navicular bone in the right hind limb, with an abnormally shaped distal phalanx and navicular bone in the left hind limb. Scintigraphic findings were closely correlated with the radiographic findings. Radiographic and scintigraphic findings were confirmed at postmortem examination.

Syndactylism and brachygnathia in a white-tailed deer

A white-tailed deer (Odocoileus virginianus) fawn was presented to the Southeastern Cooperative Wildlife Disease Study for examination of brachygnathia and syndactylous front feet. The hoof keratin of digits 3 and 4 was completely fused and typical sole integument covered the palmar surface between the primary digits. Based on a radiographic examination, there was fusion of the epiphyses of the first phalanges of digits 3 and 4 in both feet. In the right foot the proximal metaphyses of the first phalanges of digits 3 and 4 were fused.

[An unusual combination of different organ and skeletal abnormalities in a black and white calf]

This is a case report of a rare malformation in a calf: duplicitas posterior incompleta in combination with multiple malformations (diphallia, polymelia, polydactylism, lack of the bony floor of the pelvis, asymmetrical pelvis, asymmetrical sacral and coccygeal vertebrae, unilateral hypoplasia of the kidneys). A detailed description of the clinical and pathological findings is presented.

Evaluation of the hoof and foot relevant to purchase

The equine hoof and foot are the most commonly affected anatomic sites of lameness encountered during purchase examination of the performance horse. This article presents a thorough, systematic approach to the clinical evaluation of the hoof and foot relevant to the pre-purchase examination. Normal and abnormal conditions are discussed with reference to their potential effects on future performance and soundness. Proper trimming, balancing, and shoeing principles are emphasized.

Haemorrhagic claw lesions in newborn piglets due to selenium toxicosis during pregnancy

In a sow herd piglets were born with haemorrhagic lesions on the proximal wall and sole of the claws of all their feet due to abnormal horn formation. High concentrations of selenium were detected in the liver and kidney of the piglets and appeared to be associated with these lesions. A selenium rich premix added to the rations of the sows in the second half of gestation was the origin of this selenium intoxication.

Supplementary biotin for sows: effect on claw integrity

Eighty female pigs were fed, from 25 kg liveweight, either basal diets calculated to provide 32 micrograms available biotin/kg (control diet) or basal diets supplemented with 350 micrograms biotin/kg. Their claws were examined and lesions recorded at 170 days of age and when each of their first four litters was weaned. The incidence of horn 'defects' (superficial bruises, abrasions and cuts in the soft heel) remained at a low level throughout the trial. Neither the number of claws affected with lesions nor the number of lesions per sow differed between treatments at 170 days of age. Between 170 days of age and first weaning the incidence of hoof lesions increased greatly. At first weaning and for the remainder of the trial biotin supplemented sows had significantly fewer claw lesions per sow than controls (P less than 0.05 or greater). The predominant injuries to the foot were cracks which occurred mainly in two associated regions, the heel/toe junction and the heel, and the sidewall and adjacent white-line region of the toe. The differences in foot damage did not result in differences in culling rate. It was concluded that supplemention of the diet of breeding sows with biotin from an early stage of development made a significant contribution to the maintenance of their horn integrity.

Measurements of bone strain in foals with altered foot balance

Two to 7 days after birth, 9 foals were anesthetized, and strain gauges were applied to lateral and medial aspects of the third metacarpal bone of the left forelimb. In 5 of these foals, strain gauges also were applied to the radius of the left forelimb. Four to 6 days later, foals were walked (5 sets of 10 to 20 strides), and compressive and tensile strains in the bone beneath strain gauges were recorded on paper and diskette. After recording base-line data, a wedge was fitted to the hoof of the limb with the strain gauges, in such a way that the lateral bearing surface was raised, and strains were recorded again. The wedge was left in place, and further recordings were made every 2 to 3 days for 10 days. At the normal walk (base-line data), the compressive strain was higher than the tensile strain in the third metacarpal bone, on the medial side of which the mean principal compressive strain was approximately twice that on the lateral surface. Immediately after application of the wedge, strain values from the medial surface of the third metacarpal bone decreased by 40%, and the lateral surface compressive strain increased by 100%. These changes gradually decreased over 10 days, at which time there was no significant difference from base-line values (P less than 0.05). Similar but much less obvious trends were observed in the radius. Abnormal hoof balance apparently had no lasting effect on compressive forces running through the limb, and the natural situation of higher compressive strain medially was restored quickly.

[Asymmetry of the digits in pigs as a hereditarily conditioned variation in the anatomic structure of the extremities]

As follows from the population statistical investigation performed within the management information system, defects of the anatomic structure of the feet occur in the pig population of all breeds and cross combinations kept in the Czech Socialist Republic: the frequency of this occurrence is relatively higher than 4.4% (1984) and 3.8% (1985) of all litters affected by some of the genetic defects. In some populations different degrees of claw asymmetry occur in more than 40% of the individuals. Environmental conditions contribute to the severity of the defect (technology, particularly the type of floor), but the disposition is genetically conditioned. Prevention should mainly be based on the negative selection of the carriers of the undesired disposition. Working on this study, we used the results of the population statistical processing of the reports on the hereditary defects of pigs and the results of our own observations. In the former case the data concerned 29,778 pig litters, in the latter case 7343 pigs of the Large White, Landrace, Duroc and Prestice Black-Pied breeds.

Hoof overgrowth in Holstein--Friesian dairy cattle

The genetic etiology of hoof overgrowth, a widespread problem in Holstein-Friesian cattle, was examined. Although all four feet are affected, the hind feet usually have a greater degree of overgrowth. There is a distinct age tendency for the trait; the younger cows' hooves grow faster than those of the older cows, but the overgrowth in older cows reaches greater proportions. Analysis of variance of chi-square frequency tests showed that there is a component of heritability involved in the expression of the trait, but that it follows a more complex model than a simple autosomal recessive gene would show.

Skin blisters and hair loss in a rat mutant called vibrissaeless

A radiation-induced autosomal recessive mutant in the rat called vibrissaeless (vb), has been described and studied. Mutants have abnormal hair growth, the hairs being reduced in number and length. Mutant animals form blisters which then erode, crust, and heal without scars. The blisters can be artificially produced by friction and result from intraepidermal separation which is suprabasilar in position. To date, we cannot correlate this abnormality in rats with any known inherited human blistering disease.

Polydactylism in a white-tailed deer from eastern Ontario

A polydactylous right front foot was collected from a white -tailed deer (Odocoileus virginianus) fawn in eastern Ontario, Canada. We determined by gross visual and radiographic examinations that the polydactylous foot had a complete extra digit in the position of the ancestral 1st digit. This is the first documented account of a perfect polydactylous condition in a North American cervid.