[Molecular genetics of development of cornea].

This paper mainly reviews sources discussed in recent years that are devoted to the genetics of corneal development. Genetically caused separation processes of corneal bud and its specification and differentiation are considered. It is shown that mutation disorders in the genes responsible for differentiation of the cornea can lead to different forms of dystrophies and other corneal disorders.

[Genetics of Lens Development].

The paper discusses the current data on the genetics of the lens development. Genetically based processes of the formation of the lens anlage, as well as its specification and differentiation, are considered. The main genes responsible for these consecutive processes of lens development are presented. Their mutational disorders can lead to the absence or underdevelopment of the lens or multiple types of cataracts.

[Regulation of face and limb development: genetic aspects]. / Geneticheskie aspekty reguliatsii razvitiia litsa i konechnostei.

The review presents recent and earlier data on genetic regulation of different morphogenetic events in diverse organisms, mainly human, murine, avian and Drosophila ones. Without repeating the numerous names of genes in these organisms, one may summarize that the sets of genes involved in the regulation of development of facial and limbal structures in different organisms are rather similar, at least overlapping to a considerable degree.

[Study of CATCH 22: genetic aspects]. / Geneticheskie aspekty izucheniia CATCH 22.

Introducing molecular genetic techniques into clinical practice has made it possible to detect del 22q11.2, an etiological factor for congenital cardiovascular diseases in CATCH 22. The authors' complex (clinical, syndromological, molecular genetic, and computed) approach to examining this group of syndromes has enabled patients at high risk for CATCH 22 to be identified. A list of gene candidates responsible for manifestations of CATCH 22 and data on how pathological phenotypes are developing in model objects are presented.

[The formation of the right and left heart ventricles from the ventricular portion of the heart tube in embryogenesis]. / Obrazovanie pravogo i levogo zheludochkov serdtsa iz ventrikuliarnoi chasti serdechnoi trubki v émbriogeneze.

It has been generally assumed that the initial rudiment of the heart ventricle is divided by the longitudinal interventricular septum into the right and left ventricles. This paper presents evidence for the hypothesis that the right and the left ventricles are produced during normal development from different sequentially located segments of the cardiac tube. These segments yielding rudiments of the right and left ventricles could be detected even during early embryogenesis. This hypothesis requires a new explanation for the process of the formation of two separate outlets from the heart ventricles.

[Gene expression specific for heart atria and ventricles]. / Spetsificheskaia dlia predserdii i zheludochkov serdtsa ékspressiia genov.

The data on the chamber-specific expression of cardiac genes in the animal and human heart are reviewed. The positional specification of atrial and ventricular gene expression observed in adults is initiated early during embryogenesis. The existence of a cascade of genes is assumed, beginning with genes whose products form an anterior-posterior gradient along the heart-forming regions or along the linear heart tube derived from these regions, and ending with genes that encode the contractile proteins and display chamber-specific expression.

[Genetic control of the early stages of cardiac development in vertebrates]. / Geneticheskii kontrol' rannikh étapov razvitiia serdtsta u pozvonochnykh.

An attempt is made to summarize the main stages of the determination and specification of the heart in chicken, mouse, and rat embryos and to show what is currently known about the genes that participate in heart formation at early developmental stages in vertebrates.

[Cells of the neural crest and their derivatives in vertebrates: the mechanisms of migration and its role in tissue formation]. / Kletki nervnogo grebnia i ikh proizvodnye u pozvonozhnykh: mekhanizmy migratsii i rol' v formirovanii tkanei.

Segregation, determination and migration of the neural crest cells have been considered in the head and trunk of birds and mammals, with special reference to segment-specific migration. The mechanisms of their migration and involvement in formation of some organs are discussed, as well as the model of "catch" of the neural crest cells proposed for explanation of the morphogenetic processes.

[Genomic imprinting and its role in Prader-Willi and Angelman syndromes]. / Genomnyi imprinting i sindromy Pradera-Villi i Endzhel'mena.

Published and our own data, included in the CHRODYS database, on the dependence of phenotypic abnormalities in mono-, di-, and trisomics at human chromosome 15 on its parental origin are reviewed. The concept is confirmed that Prader-Willi and Angelman syndromes result from the combined effect of gene or chromosome mutations impairing the expression of syndrome-specific genes and from genomic imprinting, i.e., repression of corresponding genes received from one of the parents.

[Hand dermatoglyphics in patients with isolated triphalangia and Holt-Oram syndrome]. / Dermatoglifika kistei u patsientov s izolirovannoi trifalangiei i sindromom Kholta-Orama.

A comparative analysis of dermatoglyphic prints of patients with the Holt-Oram syndrome and isolated triphalangeal thumbs was performed with control dermatoglyphics. A specific feature of the syndrome is a change in the main palmar lines and their termination on the radial border of the hand not only in the absence of the thumb but also in the case of formation of the abortive xT-line, its radiants, and the axial triradius. This trait may be considered diagnostic for the Holt-Oram syndrome. Cases of triphalangeal thumbs with preaxial polydactyly do not reveal significant changes in dermatoglyphic patterns and appear to result from partial duplication of the thumb. An isolated triphalangeal thumb may be the result of an atavistic development of homeotic transformation of the thumb.

[Pattern formation in the early embryogenesis of the clawed toad]. / Formirovanie patterna v rannem émbriogeneze shportsevoi liagushki.

Establishment of egg polarity, separation of germ layers, appearance of animal-vegetal, dorsoventral and anteroposterior axis in Xenopus laevis embryos have been considered. The control of these processes by genes coding for growth factors, protooncogenes and homeobox-containing genes has also been reviewed.

[Genetic control of segmentation processes in axial structures in vertebrates]. / Geneticheskii kontrol' protsessov segmentatsii osevykh struktur u pozvonochnykh.

The processes of segmentation of axial structures in vertebrates during early embryonic development are reviewed. These processes include the formation of neuromeres, somitomeres, cranial ganglia, and branchial arches in the head and of neuromeres, somites, spinal ganglia, and motor nerves in the body of the embryo. The class of vertebrate homeobox genes Hox is described with respect to the arrangement of these genes in four clusters, the structural and functional similarity of paralogues in gene subfamilies, and the type of Hox gene expression in the head and body. A hypothesis concerning the existence of a genetic Hox code, determining the fate of individual segments in neuroectodermal and mesenchymal derivatives, is discussed. In the context of this hypothesis, phenotypic expression of the mutant Hox genes, accompanied by the loss of their function and cases of excessive and ectopic expression of Hox genes, are analyzed. Only in such cases do mutant phenotypes demonstrate symptoms of actual homeotic transformation, in which specific segmental structures are substituted by their homologues, as has been described for homeotic mutations in Drosophila.

[The dermatoglyphic indices in human macrodactyly]. / Izuchenie dermatoglificheskikh pokazatelei pri makrodaktilii u cheloveka.

The comparative dermatoglyphic analysis of palms and fingers of seven children with different forms of macrodactyly showed that they are fairly similar to those of normal children. The differences concern certain flattening of papillary ridges and reduced parameters of the total ridge count in the patients. Only in two cases of macrodactyly an increase in the relative length of fingers was accompanied by an increase in number of epidermal ridges and in the distance between fingers. If macrodactyly is based on somatic mutations or recombinations, then, depending on the time when the resulting mutant cell clones appear (before or after the epidermal ridges are laid down), the increased size of finger rudiments will or will not affect the value of ridge count.

Dermatoglyphic analysis of polydactylies in man: identification of digital morphogenetic fields.

We analyzed dermatoglyphic patterns of patients with pre- and postaxial polydactylies. It was found that (i) an additional finger was always accompanied by the respective digital triradius, radiants and the main line, and (ii) in postaxial polydactylies a circular pattern of epidermal ridges around the 6th finger and a 2nd additional triradius are formed. On this basis it is suggested that the palmar main lines, radiants and digital triradii serve as marker structures and borders in the process of differentiation of digital morphogenetic fields out of a unitary field organized in a fashion described by a polar coordinate system model.

[Genetic regulation of limb development in vertebrates]. / Geneticheskaia reguliatsiia razvitiia konechnostei u pozvonochnykh.

The data are surveyed concerning formation of limb buds in Vertebrate, development of morphogenetic fields in limb buds, their organization based on the simple gradient model and the model of polar coordinates. Formation of the morphogenetic fields of strictly located events, such as chondrogenesis and prescheduled cell death, based on the positional information is discussed. All the stages of limb formation in Vertebrate are under genetic control, the products of some genes behaving as extracellular factors (morphogens) and those of other as cell receptors or transcriptional factors inducing activity of specific gene sets. Highly important at that are regulatory homeobox genes.

[Bilateral symmetry of the dermatoglyphic characteristics in Down's syndrome]. / Bilateral'naia simmetriia dermatoglificheskikh kharakteristik pri sindrome Dauna.

Dermatoglyphic traits were analyzed in 132 patients with Down syndrome. The level of bilateral symmetry of dermatoglyphic indices in these patients was found to be higher than in normal people (control). By this parameter, patients with Down syndrome showed lower intragroup variation than the control group. It is suggested that such difference is due to a more primitive developmental pathway.

[Dermatoglyphic changes in some human hereditary disorders: syndactyly]. / Izmenenie dermatoglifiki pri geneticheskikh narusheniiakh u cheloveka: sindaktiliia.

The dermatoglyphic hand prints from 19 patients with different types of syndactyly were analysed. It was shown that some digital triradii and palmar lines were missing and replaced by only one triradius with common radiants and one main palmar line in patients with syndactyly. With fingers fused incompletely so called zygodactylous triradius and the main Z line may appear, instead of or alongside with them. It is proposed that the position of local cell death in the interdigital spaces is determined by positional information which is expressed in the system of polar coordinates.

[The dermatoglyphic analysis of polydactyly and the segregation of the morphogenetic fields of the fingers in man]. / Dermatoglificheskii analiz polidaktilii, vydelenie morfogeneticheskikh polei pal'tsev u cheloveka.

We studied dermatoglyphic imprints of patients with preaxial or postaxial polydactyly. Development of the additional finger is shown to be always accompanied by the corresponding finger triradius and basic line; postaxial polydactylies are characterized by the circular epidermal ridges around the rudiment of the sixth finger and the presence of the second additional triradius. On the basis of these data we suggest that major lines of the palm and finger triradii serve as landmarks denoting the borders of individual morphogenetic fields of fingers during their segregation from general morphogenetic field of the hand which is related to the polar system of coordinates.

[Disorders of finger flexion crease formation in various congenital anomalies of human development]. / Narushenie formirovaniia sgibatel'nykh skladok pal'tsev pri nekotorykh vrozhdennykh anomaliiakh razvitiia u cheloveka.

Deviations in finger flexion crease formation and ridge counts were analysed in normal and deformed (Down syndrome, arthrogriposis, diastrophic dysplasia) hands. Certain interrelation was found between decrease in the ridge count and the number of the finger flexion creases in Down syndrome. The changes observed agree with the hypothesis that intersegmental borders, and later, the joints and finger flexion creases are laid out on the basis of the positional information which is directed by morphogenetic gradients. This model enables us to interpret more or less unequivocally the changes in flexion creases in patients with arthrogriposis and diastrophic dysplasia (dwarfism).

[Dermatoglyphic changes in human genetic disorders: preaxial defects of the upper limbs]. / Izmenenie dermatoglifiki pri geneticheskikh narusheniiakh u cheloveka: preaksial'nye defekty verkhnykh konechnostei.

Dermatologlyphic prints of 9 patients with preaxial (radial) hand defects were compared with control ones. A correspondence is revealed between a decrease in thumb phalanx length and a respective decrease in ridge count, on the one hand, and between the 1st metacarpal hypo- or aplasia and a decrease in palmar ridge count between the metacarpo-phalangeal and thumb flexion creases, on the other hand. An interrelation is found between the anomalies in flexion crease and respective joint formation. It is suggested, that these disorders are due to genetically determined anomalies in morphogenetic gradients which control the distribution of positional information in upper limb morphogenetic field.