Cloning of bovine LYST gene and identification of a missense mutation associated with Chediak-Higashi syndrome of cattle

Genomic regions associated with coat color in Gir cattle

Indicine cattle breeds are adapted to the tropical climate, and their coat plays an important role in this process. Coat color influences thermoregulation and the adhesion of ectoparasites and may be associated with productive and reproductive traits. Furthermore, coat color is used for breed qualification, with breeders preferring certain colors. The Gir cattle is characterized by a wide variety of coat colors. Therefore, we performed genome-wide association studies to identify candidate genes for coat color in Gir cattle. Different phenotype scenarios were considered in the analyses and regions were identified on eight chromosomes. Some regions and many candidate genes are influencing coat color in the Gir cattle, which was found to be a polygenic trait. The candidate genes identified have been associated with white spotting patterns and base coat color in cattle and other species. In addition, a possible epistatic effect on coat color determination in the Gir cattle was suggested. This is the first published study that identified genomic regions and listed candidate genes associated with coat color in Gir cattle. The findings provided a better understanding of the genetic architecture of the trait in the breed and will allow to guide future fine-mapping studies for the development of genetic markers for selection.

The lysosomal trafficking regulator "LYST": an 80-year traffic jam

Lysosomes and lysosome related organelles (LROs) are dynamic organelles at the intersection of various pathways involved in maintaining cellular hemostasis and regulating cellular functions. Vesicle trafficking of lysosomes and LROs are critical to maintain their functions. The lysosomal trafficking regulator (LYST) is an elusive protein important for the regulation of membrane dynamics and intracellular trafficking of lysosomes and LROs. Mutations to the LYST gene result in Chédiak-Higashi syndrome, an autosomal recessive immunodeficiency characterized by defective granule exocytosis, cytotoxicity, etc. Despite eight decades passing since its initial discovery, a comprehensive understanding of LYST's function in cellular biology remains unresolved. Accumulating evidence suggests that dysregulation of LYST function also manifests in other disease states. Here, we review the available literature to consolidate available scientific endeavors in relation to LYST and discuss its relevance for immunomodulatory therapies, regenerative medicine and cancer applications.

Chediak-Higashi syndrome

PURPOSE OF REVIEW

Chediak-Higashi syndrome is a rare autosomal recessive disorder characterized by congenital immunodeficiency, bleeding diathesis, pyogenic infection, partial oculocutaneous albinism, and progressive neurodegeneration. Treatment is hematopoietic stem cell transplantation or bone marrow transplantation; however, this does not treat the neurologic aspect of the disease. Mutations in the lysosomal trafficking regulator (LYST) gene were identified to be causative of Chediak-Higashi, but despite many analyses, there is little functional information about the LYST protein. This review serves to provide an update on the clinical manifestations and cellular defects of Chediak-Higashi syndrome.

RECENT FINDINGS

More recent papers expand the neurological spectrum of disease in CHS, to include hereditary spastic paraplegia and parkinsonism. Granule size and distribution in NK cells have been investigated in relation to the location of mutations in LYST. Patients with mutations in the ARM/HEAT domain had markedly enlarged granules, but fewer in number. By contrast, patients with mutations in the BEACH domain had more numerous granules that were normal in size to slightly enlarged, but demonstrated markedly impaired polarization. The role of LYST in autophagosome formation has been highlighted in recent studies; LYST was defined to have a prominent role in autophagosome lysosome reformation for the maintenance of lysosomal homeostasis in neurons, while in retinal pigment epithelium cells, LYST deficiency was shown to lead to phagosome accumulation.

SUMMARY

Despite CHS being a rare disease, investigation into LYST provides an understanding of basic vesicular fusion and fission. Understanding of these mechanisms may provide further insight into the function of LYST.

Phenotype of White Sika Deer Due to SCF Gene Structural Variation

Breeding ornamental white sika deer is a new notion that can be used to broaden the sika deer industry However, it is very rare for other coat phenotypes to occur, especially white (apart from albinism), due to the genetic stability and homogeneity of its coat color phenotype, making it difficult to breed white sika deer between species. We found a white sika deer and sequenced its whole genome. Then, the clean data obtained were analyzed on the basis of gene frequency, and a cluster of coat color candidate genes containing 92 coat color genes, one SV (structure variation), and five nonsynonymous SNPs (single nucleotide polymorphisms) was located. We also discovered a lack of melanocytes in the skin tissue of the white sika deer through histological examination, initially proving that the white phenotype of sika deer is caused by a 10.099 kb fragment deletion of the SCF gene(stem cell factor). By designing SCF-specific primers to detect genotypes of family members of the white sika deer, and then combining them with their phenotypes, we found that the genotype of the white sika deer is SCF⁷⁸⁹/SCF⁷⁸⁹, whereas that of individuals with white patches on their faces is SCF⁷⁸⁹/SCF^1-9. All these results showed that the SCF gene plays an important role in the development of melanocytes in sika deer and is responsible for the appearance of the white coat color. This study reveals the genetic mechanism of the white coat color in sika deer and supplies data as a reference for breeding white ornamental sika deer.

Causative alleles for chondrodysplastic dwarfism, factor XI deficiency, and factor XIII deficiency in the Kumamoto sub-breed of Japanese Brown cattle

Japanese Brown cattle are the second most popular Wagyu breed, and the Kumamoto sub-breed shows better daily gain and carcass weight. One of the breeding objectives for this sub-breed is to reduce genetic defects. Chondrodysplastic dwarfism and factor VIII deficiency have been identified as genetic diseases in the Kumamoto sub-breed. Previously, we detected individuals in the Kumamoto sub-breed with causative alleles of genetic diseases identified in Japanese Black cattle. In the current study, 11 mutations responsible for genetic diseases in the Wagyu breeds were analyzed to evaluate the risk of genetic diseases in the Kumamoto sub-breed. Genotyping revealed the causative mutations of chondrodysplastic dwarfism, factor XI deficiency, and factor XIII deficiency and suggested the appearance of affected animals in this sub-breed. DNA testing for these diseases is needed to prevent economic loses in beef production using the Kumamoto sub-breed.

PMEL p.Leu18del dilutes coat color of Kumamoto sub-breed of Japanese Brown cattle

Background

Coat color is important for registration and maintenance of livestock. Standard coat color of Kumamoto sub-breed of Japanese Brown cattle is solid brown, but individuals with diluted coat color have been observed recently. In this study, we attempted to identify polymorphism(s) responsible for coat color dilution by whole genome analysis.

Results

One of the diluted cattle possessed 7302 exonic polymorphisms which could affect genes’ function. Among them, 14 polymorphisms in 10 coat color-related genes were assumed to be specific for the diluted cattle. Subsequent genotyping with three diluted cattle and 74 standard cattle elucidated that PMEL p.Leu18del was the causative polymorphism for coat color dilution in this sub-breed. Individuals with del/del type of this polymorphism showed diluted coat color, but coat color of heterozygotes were intermediate with various dilution rates.

Conclusions

Coat color dilution of Kumamoto sub-breed was caused by PMEL p.Leu18del. The causative del allele has been detected in several genetically distant cattle breeds, suggesting that PMEL p.Leu18del can be used as a DNA marker to control cattle coat color.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08916-8.

Identification of deleterious recessive haplotypes and candidate deleterious recessive mutations in Japanese Black cattle

Intensive use of a few elite sires has increased the risk of the manifestation of deleterious recessive traits in cattle. Substantial genotyping data gathered using single-nucleotide polymorphism (SNP) arrays have identified the haplotypes with homozygous deficiency, which may compromise survival. We developed Japanese Black cattle haplotypes (JBHs) using SNP array data (4843 individuals) and identified deleterious recessive haplotypes using exome sequencing of 517 sires. We identified seven JBHs with homozygous deficiency. JBH_10 and JBH_17 were associated with the resuming of estrus after artificial insemination, indicating that these haplotypes carried deleterious mutations affecting embryonic survival. The exome data of 517 Japanese Black sires revealed that AC_000165.1:g.85341291C>G of IARS in JBH_8_2, AC_000174.1:g.74743512G>T of CDC45 in JBH_17, and a copy variation region (CNVR_27) of CLDN16 in JBH_1_1 and JBH_1_2 were the candidate mutations. A novel variant AC_000174.1:g.74743512G>T of CDC45 in JBH_17 was located in a splicing donor site at a distance of 5 bp, affecting pre-mRNA splicing. Mating between heterozygotes of JBH_17 indicated that homozygotes carrying the risk allele died around the blastocyst stage. Analysis of frequency of the CDC45 risk allele revealed that its carriers were widespread throughout the tested Japanese Black cattle population. Our approach can effectively manage the inheritance of recessive risk alleles in a breeding population.

A genome-wide association study reveals a quantitative trait locus for calf mortality on chromosome 9 in Japanese Black cattle

Calf mortality is a major problem affecting cattle production. To identify genetic variants associated with calf mortality in Japanese Black cattle, we evaluated calf mortality as a categorical trait using a threshold model and conducted a GWAS. We identified two SNPs between 32 549 297 and 32 606 924 bp on bovine chromosome 9 that were significantly associated with calf mortality from 61 to 180 days after birth. The SNP showing the highest association was localized at a region 624 bp downstream of exon 4 of the anti-silencing function 1A histone chaperone gene (ASF1A) that promotes DNA damage repair, and the null mice, which exhibit pre- and postnatal lethality. This association was also detected using the breeding value of 334 sires. The frequency of the risk allele in Japanese Black cattle from locations across Japan was 0.013; although the frequency of ASF1A risk allele was low, it is widespread in the Japanese Black cattle population. Thus, it may be necessary to routinely monitor the cattle population for the presence of this allele.

Differences in melanin type and content among color variations in American mink (Neovison vison)

Coat colour is one of the most important qualitative traits of fur animals. Determining melanin pigments forming the basics of visible coat colour may contribute to a better understanding of the process of creating different coat colour variations in fur-bearing animals. This study aimed to (i) isolate pigment cells from the hair of American mink of 11 colour variations (standard brown, silverblue, palomino, black, wild type, sapphire, black cross, pearl, palomino cross, glow, and amber) using acid and alkali; and (ii) characterise the melanin pigments obtained. The purified pigment cells were observed under a light microscope and verified by spectrophotometry scanning and nuclear magnetic resonance spectroscopy. The method allowed for obtaining pure melanin specimens. Using acid and alkali to extract eumelanosomes did not affect their shape and structure; it also allowed for obtaining pheomelanin from the hair. The results have proven that the hair colour of the American mink is based on all types of melanin, and that its variations differ in terms of how much eumelanin and pheomelanin the hair contains.

Assisted reproduction mediated resurrection of a feline model for Chediak-Higashi syndrome caused by a large duplication in LYST

Chediak-Higashi Syndrome (CHS) is a well-characterized, autosomal recessively inherited lysosomal disease caused by mutations in lysosomal trafficking regulator (LYST). The feline model for CHS was originally maintained for ~20 years. However, the colonies were disbanded and the CHS cat model was lost to the research community before the causative mutation was identified. To resurrect the cat model, semen was collected and cryopreserved from a lone, fertile,  CHS carrier male. Using cryopreserved semen, laparoscopic oviductal artificial insemination was performed on three queens, two queens produced 11 viable kittens. To identify the causative mutation, a fibroblast cell line, derived from an affected cat from the original colony, was whole genome sequenced. Visual inspection of the sequence data identified a candidate causal variant as a ~20 kb tandem duplication within LYST, spanning exons 30 through to 38 (NM_001290242.1:c.8347-2422_9548 + 1749dup). PCR genotyping of the produced offspring demonstrated three individuals inherited the mutant allele from the CHS carrier male. This study demonstrated the successful use of cryopreservation and assisted reproduction to maintain and resurrect biomedical models and has defined the variant causing Chediak-Higashi syndrome in the domestic cat.

Genotypes and allele frequencies of buried SNPs in a bovine single-nucleotide polymorphism array in Japanese Black cattle

Single nucleotide polymorphism (SNP) arrays are widely used for genetic and genomic analyses in cattle breeding; thus, data derived from SNP arrays have accumulated on a large scale nationwide. Commercial SNP arrays contain a considerable number of unassigned SNPs on the chromosome/position on the genome; these SNPs are excluded in subsequent analyses. Notably, the position-unassigned SNPs, or "buried SNPs" include some of the markers associated with genetic disease. In this study, we identified the position of buried SNPs using the Basic Local Alignment Search Tool against the surrounding sequences and characterized the relationship between SNPs and genetic diseases in Online Mendelian Inheritance in Animals based on the genomic position. We determined the position of 285 buried SNPs on the genome and surveyed the genotype and allele frequencies of these SNPs in 5,955 individual Japanese Black cattle. Eleven SNPs associated with genetic disease, which contained five buried SNPs, were found in the population with the risk allele frequency ranging from 0.00008396 to 0.46. These results indicate that buried SNPs in the bovine SNP array can be utilized to identify associations with genetic disorders from large scale accumulated SNP genotype data in Japanese Black cattle.

Population genomics reveal recent speciation and rapid evolutionary adaptation in polar bears

Polar bears are uniquely adapted to life in the High Arctic and have undergone drastic physiological changes in response to Arctic climates and a hyper-lipid diet of primarily marine mammal prey. We analyzed 89 complete genomes of polar bear and brown bear using population genomic modeling and show that the species diverged only 479-343 thousand years BP. We find that genes on the polar bear lineage have been under stronger positive selection than in brown bears; nine of the top 16 genes under strong positive selection are associated with cardiomyopathy and vascular disease, implying important reorganization of the cardiovascular system. One of the genes showing the strongest evidence of selection, APOB, encodes the primary lipoprotein component of low-density lipoprotein (LDL); functional mutations in APOB may explain how polar bears are able to cope with life-long elevated LDL levels that are associated with high risk of heart disease in humans.

A new method for rapid detection of the mutant allele for Chediak-Higashi syndrome in Japanese black cattle

Chediak-Higashi syndrome (CHS) is an autosomal recessive hereditary disorder in Japanese Black cattle, caused by a mutation of the Lyst gene. So far, the mutation has been detected by PCR-restriction fragment length polymorphism (PCR-RFLP) analysis. However, this method is disadvantaged by its low-throughput performance. Here, we report an alternative method involving real-time PCR with TaqMan minor groove binder probes, which shortens the total assay time by more than 120 min, analyzing 10 samples in a duplicated manner. Using this method, we examined 102 Japanese Black cattle and found that 8.8% of the cattle were CHS-carriers. These data indicate that our technique is useful for routine diagnostic testing for CHS in Japanese Black cattle.

Pleiotropic effects of coat colour-associated mutations in humans, mice and other mammals

The characterisation of the pleiotropic effects of coat colour-associated mutations in mammals illustrates that sensory organs and nerves are particularly affected by disorders because of the shared origin of melanocytes and neurocytes in the neural crest; e.g. the eye-colour is a valuable indicator of disorders in pigment production and eye dysfunctions. Disorders related to coat colour-associated alleles also occur in the skin (melanoma), reproductive tract and immune system. Additionally, the coat colour phenotype of an individual influences its general behaviour and fitness. Mutations in the same genes often produce similar coat colours and pleiotropic effects in different species (e.g., KIT [reproductive disorders, lethality], EDNRB [megacolon] and LYST [CHS]). Whereas similar disorders and similar-looking coat colour phenotypes sometimes have a different genetic background (e.g., deafness [EDN3/EDNRB, MITF, PAX and SNAI2] and visual diseases [OCA2, RAB38, SLC24A5, SLC45A2, TRPM1 and TYR]). The human predilection for fancy phenotypes that ignore disorders and genetic defects is a major driving force for the increase of pleiotropic effects in domestic species and laboratory subjects since domestication has commenced approximately 18,000 years ago.

A nonsense mutation in the tyrosinase gene causes albinism in water buffalo

Background

Oculocutaneous albinism (OCA) is an autosomal recessive hereditary pigmentation disorder affecting humans and several other animal species. Oculocutaneous albinism was studied in a herd of Murrah buffalo to determine the clinical presentation and genetic basis of albinism in this species.

Results

Clinical examinations and pedigree analysis were performed in an affected herd, and wild-type and OCA tyrosinase mRNA sequences were obtained. The main clinical findings were photophobia and a lack of pigmentation of the hair, skin, horns, hooves, mucosa, and iris. The results of segregation analysis suggest that this disease is acquired through recessive inheritance. In the OCA buffalo, a single-base substitution was detected at nucleotide 1,431 (G to A), which leads to the conversion of tryptophan into a stop codon at residue 477.

Conclusion

This premature stop codon produces an inactive protein, which is responsible for the OCA buffalo phenotype. These findings will be useful for future studies of albinism in buffalo and as a possible model to study diseases caused by a premature stop codon.

A frameshift mutation in the LYST gene is responsible for the Aleutian color and the associated Chédiak-Higashi syndrome in American mink

One of the colors of mink is Aleutian (aa)-a specific gun-metal gray pigmentation of the fur-commonly used in combination with other color loci to generate popular colors such as Violet (aammpp) and Sapphire (aapp). The Aleutian color allele is a manifestation of mink Chédiak-Higashi syndrome (CHS), which has been described in humans and several other species. As with forms of CHS in other species, we report that the mink CHS is linked to the lysosomal trafficking regulator ( LYST ) gene. Furthermore, we have identified a base deletion (c.9468delC) in exon 40 of LYST, which causes a frameshift and virtually terminates the LYST product prematurely (p.Leu3156Phefs*37). We investigated the blood parameters of three wild-type mink and three CHS mink. No difference in the platelet number between the two groups was observed, but an accumulation of platelets between the groups appears different when collagen is used as a coagulant. Microscopic analysis of peripheral blood indicates giant inclusions in the neutrophils of the Aleutian mink types. Molecular findings at the LYST locus enable the development of genetic tests for analyzing the color selection in American mink.

Inherited platelet disorders

OBJECTIVE

To present the latest information on inherited platelet disorders in domestic animals.

DATA SOURCES

Research articles and reviews spanning 40 years available on PubMed.

HUMAN DATA SYNTHESIS

Information regarding inherited platelet disorders in people is plentiful and often descriptions of human conditions have led to the identification of similar disorders in veterinary species. There are exceptions, however, in which specific inherited platelet disorders were first described in animals with subsequent identification in people.

VETERINARY DATA SYNTHESIS

Many inherited platelet disorders have been documented in animals at the functional and molecular level and that information is presented in this review.

CONCLUSIONS

Much progress has been made in the past 20 years in the characterization of inherited platelet disorders in animals at the functional, biochemical, and molecular level. The study of inherited platelet disorders has greatly enhanced the understanding of platelet physiology and has led in some instances to the development of platelet inhibitory medications. Characterization of inherited disorders at the molecular level greatly facilitates diagnosis and identification of affected and heterozygous animals thus avoiding propagation of the defect by breeders. When used with available functional and biochemical diagnostic tests, it significantly enhances the quality of care and case management.

Potential large animal models for gene therapy of human genetic diseases of immune and blood cell systems

Genetic mutations involving the cellular components of the hematopoietic system--red blood cells, white blood cells, and platelets--manifest clinically as anemia, infection, and bleeding. Although gene targeting has recapitulated many of these diseases in mice, these murine homologues are limited as translational models by their small size and brief life span as well as the fact that mutations induced by gene targeting do not always faithfully reflect the clinical manifestations of such mutations in humans. Many of these limitations can be overcome by identifying large animals with genetic diseases of the hematopoietic system corresponding to their human disease counterparts. In this article, we describe human diseases of the cellular components of the hematopoietic system that have counterparts in large animal species, in most cases carrying mutations in the same gene (CD18 in leukocyte adhesion deficiency) or genes in interacting proteins (DNA cross-link repair 1C protein and protein kinase, DNA-activated catalytic polypeptide in radiation-sensitive severe combined immunodeficiency). Furthermore, we describe the potential of these animal models to serve as disease-specific preclinical models for testing the efficacy and safety of clinical interventions such as hematopoietic stem cell transplantation or gene therapy before their use in humans with the corresponding disease.

Linkage mapping of the locus responsible for forelimb-girdle muscular anomaly of Japanese black cattle on bovine chromosome 26

Forelimb-girdle muscular anomaly is an autosomal recessive disorder of Japanese black cattle characterized by tremor, astasia and abnormal shape of the shoulders. Pathological examination of affected animals reveals hypoplasia of forelimb-girdle muscles with reduced diameter of muscle fibres. To identify the gene responsible for this disorder, we performed linkage mapping of the disorder locus using an inbred pedigree including a great-grand sire, a grand sire, a sire and 26 affected calves obtained from a herd of Japanese black cattle. Two hundred and fifty-eight microsatellite markers distributed across the genome were genotyped across the pedigree. Four markers on the middle region of bovine chromosome 26 showed significant linkage with the disorder locus. Haplotype analysis using additional markers in this region refined the critical region of the disorder locus to a 3.5-Mb interval on BTA26 between BM4505 and MOK2602. Comparative mapping data revealed several potential candidate genes for the disorder, including NRAP, PDZD8 and HSPA12A, which are associated with muscular function.

Alteration of release and role of adenosine diphosphate and thromboxane A2 during collagen-induced aggregation of platelets from cattle with Chediak-Higashi syndrome

OBJECTIVE

To compare the interaction of endogenous ADP with collagen and thromboxane A(2) (TXA(2)) during collagen-induced platelet aggregation between platelets from healthy cattle and those with Chediak-Higashi syndrome (CHS). POPULATION SAMPLE: Platelets harvested from blood samples from healthy Japanese Black cattle and those with CHS.

PROCEDURES

Aggregation of gel-filtered platelets; release of ATP-ADP; and generation of thromboxane B(2) (TXB(2)), a metabolite of TXA(2), were measured.

RESULTS

The potency of collagen to induce aggregation in platelets of cattle with CHS (ie, CHS platelets) was less than a tenth of that in platelets of healthy cattle (ie, control platelets). Platelet aggregation induced by collagen at an intermediate concentration depended on the coexistence of ADP and TXA(2), suggesting that released ADP cannot cause platelet aggregation by itself. Collagen-induced ADP release was markedly decreased, whereas TXB(2) production was slightly low in CHS platelets, compared with that in control platelets. A combination of subthreshold amounts of ADP and 9,11-dideoxy-9alpha, 11alpha-methano-epoxy-prostaglandin F(2) (U46619), a TXA(2) analogue, caused platelet aggregation. Similarly, a combination of subthreshold amounts of collagen and ADP caused platelet aggregation, whereas collagen and U46619 were not synergistic.

CONCLUSIONS AND CLINICAL RELEVANCE

Deficient ADP release ensuing from the delta-storage pool deficiency in platelets from cattle with CHS resulted in reduction of collagen-induced platelet aggregation, through attenuation of synergism between TXA(2) and ADP and between ADP and collagen. Furthermore, results of the study reported here indicated that TXA(2) was important for aggregation of bovine platelets.

A missense mutation in the WD40 domain of murine Lyst is linked to severe progressive Purkinje cell degeneration

Disturbance of intracellular trafficking plays a major role in several neurodegenerative disorders including Alzheimer or Parkinson's disease. The Chediak-Higashi syndrome (CHS), a life-threatening autosomal recessive disease with frequent mutations in the LYST gene, and its animal model, the beige mouse, are both characterized by lysosomal defects with accumulation of giant lysosomes. Clinically they manifest as hypopigmentation, abnormal bleeding and increased susceptibility to infection with various degrees of involvement of the nervous system. In the course of a recessive N-ethyl-N-nitrosurea (ENU) mutagenesis screen, we identified the first murine missense mutation in the lysosomal trafficking regulator gene (Lyst(Ing3618)) located at a highly conserved position in the WD40 protein domain. Nearly all described human Lyst alleles lead to protein truncation and fatal childhood CHS. Only four different missense mutations have been reported in patients with adolescent or adult forms of CHS involving the nervous system. Interestingly, the Lyst(Ing3618) model presents with a predominant neurodegenerative phenotype with progressive degeneration and loss of Purkinje cells and lacks severe impairment of the immune system. Therefore, the Lyst(Ing3618 )allele could represent a new model for adult CHS with neurological impairment. It could also provide an important tool to elucidate the role of neuronal lysosomal trafficking in the pathophysiology of neurodegeneration.

Grey, a novel mutation in the murine Lyst gene, causes the beige phenotype by skipping of exon 25

The murine beige mutant phenotype and the human Chediak-Higashi syndrome are caused by mutations in the murine Lyst (lysosomal trafficking regulator) gene and the human CHS gene, respectively. In this report we have analyzed a novel murine mutant Lyst allele, called Lyst(bg-grey), that had been found in an ENU mutation screen and named grey because of the grey coat color of affected mice. The phenotype caused by the Lyst(bg-grey) mutation was inherited in a recessive fashion. Melanosomes of melanocytes associated with hair follicles and the choroid layer of the eye, as well as melanosomes in the neural tube-derived pigment epithelium of the retina, were larger and irregularly shaped in homozygous mutants compared with those of wild-type controls. Secretory vesicles in dermal mast cells of the mutant skin were enlarged as well. Test crosses with beige homozygous mutant mice (Lyst(bg)) showed that double heterozygotes (Lyst(bg)/Lyst(bg-grey)) were phenotypically indistinguishable from either homozygous parent, demonstrating that the ENU mutation was an allele of the murine Lyst gene. RT-PCR analyses revealed the skipping of exon 25 in Lyst(bg-grey) mutants, which is predicted to cause a missense D2399E mutation and the loss of the following 77 amino acids encoded by exon 25 but leave the C-terminal end of the protein intact. Analysis of the genomic Lyst locus around exon 25 showed that the splice donor at the end of exon 25 showed a T-to-C transition point mutation. Western blot analysis suggests that the Lyst(bg-grey) mutation causes instability of the LYST protein. Because the phenotype of Lyst(bg) and Lyst(bg-grey) mutants is indistinguishable, at least with respect to melanosomes and secretory granules in mast cells, the Lyst(bg-grey) mutation defines a critical region for the stability of the murine LYST protein.

Linkage mapping of the locus responsible for congenital multiple ocular defects in cattle on bovine Chromosome 18

Congenital multiple ocular defects (MOD) in Japanese black cattle is a hereditary ocular disorder with an autosomal recessive manner of inheritance, showing developmental defects of the lens, retina, and iris, persistent embryonic eye vascularization, and microphthalmia. In the present study, we mapped the locus responsible for the disorder by linkage analysis using 240 microsatellite markers covering the entire bovine genome and an inbred pedigree obtained from commercial herds. The linkage analysis demonstrated a significant linkage between the disorder locus and markers on the proximal region of bovine Chromosome (BTA) 18 with the maximum LOD score of 5.1. Homozygosity mapping using the haplotype of the linked markers further refined the critical region. The results revealed the localization of the locus responsible for MOD in an approximately 6.6-cM region of BTA18. Comparison of published linkage and radiation hybrid (RH) maps of BTA18 with its evolutionary ortholog, human Chromosome (HSA) 16, revealed several potential candidate genes for the disorder including the MAF and FOXC 2 genes.

Platelet dysfunction in Chediak-Higashi syndrome-affected cattle

A serious symptom of cattle affected with Chediak-Higashi syndrome (CHS) is a bleeding tendency. This diathesis is characterized by insufficient platelet aggregation as a result of depressed response to collagen. One possible cause for the depression is a decrease in contribution of endogenous agonists such as ADP or thromboxane A(2), which are released following collagen stimulation. However, these endogenous agonists play only a minor role in collagen-induced aggregation of bovine platelets. More importantly, activation of phospholipase C as a result of a direct action of collagen is depressed, leading to a depression of Ca(2+) mobilization, in platelets from CHS-affected cattle. Several types of collagen receptor are proposed to work in concert to induce aggregation. Among them, glycoprotein VI (GPVI) and GPIa/IIa (integrin alpha2 beta1) have been supposed to play dominant roles in collagen-induced aggregation. However, there are arguments about the role of each receptor, especially the role of GPIa/IIa, and the crosstalk between receptors. Recently, we reported that the Ca(2+) signaling produced by rhodocytin, which had been first reported to be an agonist for the collagen receptor GPIa/IIa, produced much less Ca(2+) signaling in CHS platelets than in normal ones, whereas that produced by GPVI activators was normal. These suggest that GPIa/IIa or the rhodocytin-associated pathway is impaired in CHS platelets. CHS platelets are valuable to reassess the mechanism of collagen-dependent signal transduction system and to delineate the inter-relationship among collagen receptors.

Chediak-Higashi Syndrome: a rare disorder of lysosomes and lysosome related organelles

Chediak-Higashi Syndrome (CHS) is a rare autosomal recessive disorder characterized by severe immunologic defects including recurrent bacterial infections, impaired chemotaxis and abnormal natural killer (NK) cell function. Patients with this syndrome exhibit other symptoms such as an associated lymphoproliferative syndrome, bleeding tendencies, partial albinism and peripheral neuropathies. The classic diagnostic feature of CHS is the presence of huge lysosomes and cytoplasmic granules within cells. Similar defects are found in other mammals, the most well studied being the beige mouse and Aleutian mink. A positional cloning approach resulted in the identification of the Beige gene on chromosome 13 in mice and the CHS1/LYST gene on chromosome 1 in humans. The protein encoded by this gene is 3801 amino acids and is highly conserved throughout evolution. The identification of CHS1/Beige has defined a family of genes containing a common BEACH motif. The function of these proteins in vesicular trafficking remains unknown.

Analysis of the lysosomal storage disease Chediak-Higashi syndrome

Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disorder of human, mouse (beige) and other mammalian species. The same genetic defect was found to result in the disease in all species identified, permitting a positional cloning approach using the mouse model beige to identify the responsible gene. The CHS gene was cloned and mutations identified in affected species. This review discusses the clinical features of CHS contrasting features seen in similar syndromes. The possible functions of the protein encoded by the CHS/beige gene are discussed, along with the alterations in cellular physiology seen in mutant cells.

A deletion of the paracellin-1 gene is responsible for renal tubular dysplasia in cattle

Various hereditary diseases analogous to particular human heritable diseases have been identified in cattle. Investigation of these cattle diseases will provide useful information regarding the pathogenesis of the corresponding human diseases. Renal tubular dysplasia is an autosomal recessive disease of Japanese black cattle characterized by renal failure and growth retardation. We have previously mapped the locus responsible for the disease within a region on bovine chromosome 1. In the present study, we further typed additional markers in this region and found that a genomic segment of bovine chromosome 1 including the microsatellite marker BMS4009 was deleted in the affected animals. Construction of a physical map covering this region with BAC clones and comparison of the nucleotide sequences of this region between normal and affected animals revealed that a region of 37 kb including exons 1 to 4 of the bovine paracellin-1 gene was deleted in the affected animals. The paracellin-1 gene, which is the causative gene for human renal hypomagnesemia with hypercaciuria and nephrocalcinosis, encodes a tight junction protein of renal epithelial cells. Therefore, we concluded that deletion of the paracellin-1 gene is responsible for renal tubular dysplasia of cattle, and the cattle disease could be a good model for the human disease.