Differentiating among horse (Equus caballus), donkey (Equus asinus) and their hybrids with combined analysis of nuclear and mitochondrial gene polymorphism

Identification of Five Gelatins Based on Marker Peptides from Type I Collagen by Mass Spectrum in Multiple Reaction Monitoring Mode

In this study, a novel pseudo-targeted peptidomics strategy, integrating the transition list generated by an in-house software (Pep-MRMer) and the retention time transfer by high-abundance ion-based retention time calibration (HAI-RT-cal), was developed to screen marker peptides of gelatins from five closely related animal species, including porcine, bovine, horse, mule, and donkey. Five marker peptides were screened from the molecular phenotypic differences of type I collagen. Furthermore, a simple and robust 10 min multiple reaction monitoring (MRM) method was established and performed well in distinguishing different gelatins, particularly in discerning horse-hide gelatin (HHG) and mule-hide gelatin (MHG) from donkey-hide gelatin (DHG). The market investigation revealed the serious adulteration of DHG. Meantime, the pseudo-targeted peptidomics could be used to screen marker peptides of other gelatin foods.

Species-specific identification of donkey-hide gelatin and its adulterants using marker peptides

Donkey-hide gelatin is an important traditional Chinese medicine made from donkey skin. Despite decades of effort, identifying the animal materials (donkeys, horses, cattle and pigs) in donkey-hide gelatin remains challenging. In our study, we aimed to identify marker peptides of donkey-hide gelatin and its adulterants and develop a liquid chromatography–tandem mass spectrometry method to identify them. Theoretical marker peptides of four animals (donkeys, horses, cattle and pigs) were predicted and verified by proteomic experiments, and 12 species-specific marker peptides from donkey-hide gelatin and its adulterants were identified. One marker peptide for each gelatin was selected to develop the liquid chromatography–tandem mass spectrometry method. The applicability of the method was evaluated by investigating homemade mixed gelatin samples and commercial donkey-hide gelatin products. Using the liquid chromatography–tandem mass spectrometry method, the addition of cattle-hide gelatin and pig-hide gelatin to donkey-hide gelatin could be detected at a level of 0.1%. Horse-hide gelatin was detected when added at a level of 0.5%. Among 18 batches of donkey-hide gelatin products, nine were identified as authentic, and eight of the remaining samples were suspected to be adulterated with horse materials. These results provide both a practical method to control the quality of donkey-hide gelatin and a good reference for quality evaluations of other medicinal materials and foods containing protein components.

Species assignment in forensics and the challenge of hybrids

Forensic identification of species is in growing demand, particularly from law enforcement authorities in the areas of wildlife, fisheries and hunting as well as food authentication. Within the non-human forensic genetics expanding applications' field, the major current difficulties result from the lack of standards and genetic databases as well as the poor or absent taxonomic definition of several groups. Here we focus on a forensically important and overlooked problem in species identification: the exclusive use of uniparental markers, a common practice in current genetic barcoding methodologies, may lead to incorrect or impossible assignment whenever hybrids can occur (frequently, not only in domesticates, but also in the wild). For example, if one of these cases involves a mammal, and mitochondrial DNA alone is used (which in instances may be the only type of DNA sequence available in databases), the sample will be wrongfully assigned to the female parental species, completely missing the detection of a possible hybrid animal. The importance of this issue in the forensic contributions to food authentication, wildlife and conservation genetics is analyzed. We present a cautionary guidance on the forensic reporting of results avoiding this error.

Specific, sensitive and rapid authentication of donkey-hide gelatine (Colla corii asini) in processed food using an isothermal nucleic acid amplification assay

Donkey-hide gelatine (DHG) is a well-known, animal-derived traditional Chinese medicine material called Colla corii asini (known in Chinese as "E'jiao"). Because DHG is claimed to have properties that are beneficial to health, its consumption has increased, but its production has decreased. Thus, the incidence of DHG adulteration has become increasingly serious. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the authentication of DHG. Identification of donkey DNA from DHG was performed specifically and rapidly within one hour by LAMP primers. Moreover, the sensitivity of LAMP in authenticating DHG was 10^-3 ng, which revealed a 10⁵-fold higher sensitivity than that of conventional PCR. The relative detection limit was 0.1% DHG in the adulterants, including gelatines of horse, cow, pork, goat, sheep or chicken origins. When genomic DNAs extracted from heat-treated DHG samples, including boiling or autoclaving for 40 min, were used as templates, DHG detection by LAMP was unchanged and reproducible. In conclusion, the LAMP assay established herein could potentially be applied for the authentication of DHG and DHG-related products in herbal or food markets.

Identification of the Adulterated Asini Corii Colla with Cytochrome c Oxidase Subunit I Gene-based Polymerase Chain Reaction

Background:

Asini Corii Colla (ACC) (namely donkey hide gelatin, E'jiao in Chinese) was one of the most valuable tonic traditional Chinese medicines which is an infallible remedy to promote hematopoiesis. It should be produced by fresh or dried donkey hide according to Chinese Pharmacopeia (2015 edition) with a long-time decoction, while as donkey and horse (or mule) all belong to equids so their hides or their hide gelatins are share much in common, that cause the difficult in distinguishing raw materials donkey hide from horse/mule hide for manufacturer, and the challenge in the quality evaluation of ACC for regulatory authority to identify the adulterated with horse hide.

Objective:

To establish an effective quality evaluation methods for ACC focused on the qualitative-based identification of the raw material's authenticity, mainly to identify the species origin of the gelatins.

Materials and Methods:

DNA extracted from (1) Raw materials (hides of donkey, horse, mule, bovine and pig); (2) Five hide-glues (bovine, pig, donkey, horse and mule hide-glue); (3) 11 batches of ACC commercial products made by different manufactures from local drug stores. Polymerase chain reaction (PCR) method with newly designed horse-specific primers I and primer pair II.

Results:

Use the primer pair I, a 234 bp target product could be amplified sensitively from the DNA sample of horse/mule adulterated commercial ACC products, though the DNA in commercial products is severely degraded. A 219 bp product could be amplified specifically from the DNA sample of horse/mule hide, while the results were all negative for the DNA templates of donkey hide, its gelatin and ACC products without adulteration.

Conclusion:

The developed PCR method based on primer I and II provide an effective approach to identify the species origin of highly processed product ACC (primer pair I) as well as to distinguish the raw material donkey hide (primer pair II), which might enlighten a new strategy to the Quality Evaluation of ACC.

SUMMARY

Though the quality of commercial Asini Corii Colla (ACC) products varies greatly and produce with nondonkey hide was one the most common adulteration, the effective method to constrain such adulteration remains to be established

The gelatins made by donkey, horse, bovine, pig, mule shares much in common with each other, not only in contents of amino acids but also the profiles of protein in sodium dodecyl sulfate polyacrylamide gel electrophoresis, isoelectric focusing, gel filtration chromatography and two-dimensional electrophoresis

The adulteration in ACC by using horse/mule hide, which is most difficult to detect, could be identified by Polymerase chain reaction methods with newly designed horse/mule-specific primer.

Abbreviations Used: ACC: Asini Corii Colla; TCMs: Traditional Chinese Medicines; SDS-PAGE: Sodium dodecyl sulfate polyacrylamide gel electrophoresis; IEF: Isoelectric focusing; GFC: Gel filtration chromatography; 2-DE: Two-dimensional electrophoresis; PCR: Polymerase chain reaction

Testicular Characteristics and the Block to Spermatogenesis in Mature Hinny

Most hinnies (female donkey×male horse) and mules (female horse×male donkey) are sterile with few reports of equine fertile hybrids. The main cause of this sterility is thought to be a meiotic block to spermatogenesis and oogenesis. This study compared the developmental features of the testes and a histological analyses of spermatogenesis in a male hinny with those of a normal, fertile stallion and Jack donkey. Hinny testes showed a thicker tunica albuginea, fewer blood vessels and more connective tissue in the testis parenchyma than those of the stallion and Jack donkey. Although the mean number of seminiferous tubules was significantly higher in stallion and hinny than Jack donkey (p<0.01), the mean proportion of seminiferous tubules was lower in the hinny (p<0.01) which resulted in a smaller diameter of seminiferous tubules. The mean number of spermatogonia and spermatocytes per unit area were significantly lower in hinny testis (p<0.01) and no spermatids or mature spermatozoa cells were found during immunofluorescent analyses. These results indicated that defects in seminiferous tubule development and structure occur in the testis of hinnies. Furthermore, most spermatogonia and spermatocytes cease development in synapsis during mid-meiosis of spermatocytes, which results in a block to spermatogenesis that prevents the formation of spermatids and matured spermatozoa during meiosis in male hinnies.

Case-Study Investigation of Equine Maternity via PCR-RFLP: A Biochemistry Laboratory Experiment

A simple and robust biochemistry laboratory experiment is described that uses restriction fragment length polymorphism (RFLP) of polymerase chain reaction (PCR) products to verify the identity of a potentially valuable horse. During the first laboratory period, students purify DNA from equine samples and amplify two loci of mitochondrial DNA. During the second laboratory period, students digest PCR products with restriction enzymes and analyze the fragment sizes through agarose gel electrophoresis. An optional step of validating DNA extracts through realtime PCR can expand the experiment to three weeks. This experiment, which has an engaging and versatile scenario, provides students with exposure to key principles and techniques of molecular biology, bioinformatics, and evolution in a forensic context.