Uner Tan Research Articles

Quadrupedal locomotion in Uner Tan syndrome: A neurological viewpoint

Quadrupedal locomotion in Uner Tan syndrome: A neurological viewpoint

A Rare Case of Uner Tan Syndrome With Incidentally Detected Choroid Plexus Papilloma.

A Rare Case of Uner Tan Syndrome With Incidentally Detected Choroid Plexus Papilloma.

PIGG gene mutation associated with Uner Tan syndrome: A first case report

PIGG gene mutation associated with Uner Tan syndrome: A first case report

Use it or lose it? Effects of age, experience, and disuse on crawling.

What happens to early acquired but later abandoned motor skills? To investigate effects of disuse on early-developing motor skills, we examined crawling in two groups of habitual crawlers (34 6-12-month-old infants and five adults with Uner Tan Syndrome) and two groups of rusty crawlers (27 11-12-year-old children and 13 college-aged adults). Habitual crawlers showed striking similarities in gait patterns, limbs supporting the body, and crawling speed, despite dramatic differences in crawling practice, posture, and body size. Habitual crawlers trotted predominantly, whereas rusty crawlers showed a variety of gait patterns. Within sequences, habitual crawlers and children showed more switches in gait patterns than young adults. Children crawled faster and kept fewer limbs on the grounds than the other groups. Old crawling patterns were retained despite disuse, but new ones were also added. Surprisingly, results indicate that nothing was lost with disuse, but some features of crawling were gained or altered.

Sex differences in quadrupedal walking gaits of Uner Tan syndrome cases, healthy humans and nonhuman primates

Background: Uner Tan syndrome (UTS) cases with habitual quadrupedal locomotion (QL), impaired intelligence, and dysarthric or no speech predominantly use lateral sequence (LS) gait like nonprimates rather than the predominantly diagonal sequence (DS) gait of nonhuman primates. However, these studies neglected possible sex-related differences in these gait types.Objectives: (1) To assess the possible sex-related gait types in UTS cases, healthy infants and adults with requested QL, and the nonhuman primates. (2) To test the hypothesis that sex differences may exist in quadrupedal walking gaits in UTS cases, healthy humans, and nonhuman primates.Methods: The UTS cases were filmed, the other study groups were taken from public open ‘youtube’ videos, which were used to assess the walking gait types as DS and LS. The right and left hind-limb phase values were calculated separately for males and females to allow a possible sex difference in walking gaits to be determined.Results: Females predominantly used DS gait, contrary to males with predominantly LS gait.Conclusions: Consistent with the working hypothesis, the results suggested a biological sex-related trend in preferred walking gaits exists in all of the human and nonhuman primates using QL.

Uner Tan syndrome caused by a homozygous TUBB2B mutation affecting microtubule stability.

The integrity and dynamic properties of the microtubule cytoskeleton are indispensable for the development of the mammalian brain. Consequently, mutations in the genes that encode the structural component (the α/β-tubulin heterodimer) can give rise to severe, sporadic neurodevelopmental disorders. These are commonly referred to as the tubulinopathies. Here we report the addition of recessive quadrupedalism, also known as Uner Tan syndrome (UTS), to the growing list of diseases caused by tubulin variants. Analysis of a consanguineous UTS family identified a biallelic TUBB2B mutation, resulting in a p.R390Q amino acid substitution. In addition to the identifying quadrupedal locomotion, all three patients showed severe cerebellar hypoplasia. None, however, displayed the basal ganglia malformations typically associated with TUBB2B mutations. Functional analysis of the R390Q substitution revealed that it did not affect the ability of β-tubulin to fold or become assembled into the α/β-heterodimer, nor did it influence the incorporation of mutant-containing heterodimers into microtubule polymers. The 390Q mutation in S. cerevisiae TUB2 did not affect growth under basal conditions, but did result in increased sensitivity to microtubule-depolymerizing drugs, indicative of a mild impact of this mutation on microtubule function. The TUBB2B mutation described here represents an unusual recessive mode of inheritance for missense-mediated tubulinopathies and reinforces the sensitivity of the developing cerebellum to microtubule defects.

Siblings in Kars, Turkey, with Uner Tan syndrome (quadrupedal locomotion, severe mental retardation, and no speech): a novel theory for the evolution of human bipedalism

Objective:To investigate siblings from Kars (n = 2), Turkey, with diagonal-sequence quadrupedal locomotion (QL), severe mental retardation, and no speech (Uner Tan syndrome, UTS), in relation to the evolutionary emergence of human bipedal locomotion (BL).Methods:Video recordings were made to assess gaits. Brain MRI scanning was performed to visualize the cerebro-cerebellar malformations. Genome-wide association analyses were performed in venous blood samples.Results:One of the two men with UTS showed early-onset QL and late-onset BL without infantile hypotonia, the other consistent QL with infantile hypotonia. No homozygosity was found in the genetic analysis. The family lived under extremely poor socioeconomic conditions.Conclusions:Low socioeconomic status may be a triggering factor for the epigenetic emergence of UTS. The neural networks responsible for the ancestral diagonal-sequence QL, evolutionarily preserved since about 400 MYA, may be selected during locomotor development, under the influence of self-organizing processes during pre- and postnatal periods. The diagonal-sequence QL induced ipsilateral limb interference in UTS cases as in nonhuman primates. To overcome this condition, our ancestors would prefer the attractor BL. This novel theory for the evolution of human bipedalism was evaluated in light of dynamical systems theory.

Human quadrupeds, primate quadrupedalism, and Uner Tan Syndrome.

Since 2005, an extensive literature documents individuals from several families afflicted with “Uner Tan Syndrome (UTS),” a condition that in its most extreme form is characterized by cerebellar hypoplasia, loss of balance and coordination, impaired cognitive abilities, and habitual quadrupedal gait on hands and feet. Some researchers have interpreted habitual use of quadrupedalism by these individuals from an evolutionary perspective, suggesting that it represents an atavistic expression of our quadrupedal primate ancestry or “devolution.” In support of this idea, individuals with “UTS” are said to use diagonal sequence quadrupedalism, a type of quadrupedal gait that distinguishes primates from most other mammals. Although the use of primate-like quadrupedal gait in humans would not be sufficient to support the conclusion of evolutionary “reversal,” no quantitative gait analyses were presented to support this claim. Using standard gait analysis of 518 quadrupedal strides from video sequences of individuals with “UTS”, we found that these humans almost exclusively used lateral sequence–not diagonal sequence–quadrupedal gaits. The quadrupedal gait of these individuals has therefore been erroneously described as primate-like, further weakening the “devolution” hypothesis. In fact, the quadrupedalism exhibited by individuals with UTS resembles that of healthy adult humans asked to walk quadrupedally in an experimental setting. We conclude that quadrupedalism in healthy adults or those with a physical disability can be explained using biomechanical principles rather than evolutionary assumptions.

Co-Variations Among Cognition, Cerebellar Disorders and Cortical Areas With Regional Glucose-Metabolic Activities in a Homogeneous Sample with Uner Tan Syndrome: Holistic Functioning of the Human Brain

Background: Patients with Uner Tan syndrome (UTS) exhibit habitual quadrupedal locomotion (QL), intellectual disability, dysarthric speech and truncal ataxia. Examination of cognitive ability in this syndrome has not yet been demonstrated in the scientific literature. Aims: (i) To analyze the cognitive abilities of the siblings with UTS; (ii) to assess the grade of their ataxia in relation to cerebellar disorders; (iii) to measure the metabolic activities of various cerebral regions in comparison with healthy individuals; (iv) to detect the interrelationships among all of the measured variables (IQ test scores, ataxia scores, cerebro-cerebellar areas and their metabolic activity levels) to reveal the holistic activity of the brain. Methods: The Minimental State Examination (MMSE) and Wechsler Adult Intelligence Scale (WAIS-R) were applied to the affected cases and healthy subjects. Cerebellar disorders were assessed by the International Cooperative Ataxia Rating Scale (ICARS). Brain MRI scans were performed and cerebro-cerebellar areas were measured on MRI scans, including their metabolic activities (SUV), measured by positron emission tomography (PET) scanning. Results: MMSE and WAIS-R scores both correlated with cerebro-cerebellar areas. Cerebello-vermial areas and their metabolic activities were significantly smaller in patients than in normal controls; areas of the remaining structures were not significantly different between patients and healthy subjects. Brain areas significantly inter-correlated: ICARS negatively correlated with WAIS-R, MMSE scores, SUV, and cerebro-cerebellar areas, which significantly correlated with each other. Conclusions: The results suggested (i) ICARS may not only be a test for cerebellar disorders, but also may be related to global functioning of all of the cerebro-cerebellar regions; (ii) ICARS, WAIS-R and MMSE may be measures of emergent properties of the holistic activity of the brain; (iii) the psychomotor disorders in UTS may be related to decreased brain metabolism.

Two families with quadrupedalism, mental retardation, no speech, and infantile hypotonia (Uner Tan Syndrome Type-II); a novel theory for the evolutionary emergence of human bipedalism.

Two consanguineous families with Uner Tan Syndrome (UTS) were analyzed in relation to self-organizing processes in complex systems, and the evolutionary emergence of human bipedalism. The cases had the key symptoms of previously reported cases of UTS, such as quadrupedalism, mental retardation, and dysarthric or no speech, but the new cases also exhibited infantile hypotonia and are designated UTS Type-II. There were 10 siblings in Branch I and 12 siblings in Branch II. Of these, there were seven cases exhibiting habitual quadrupedal locomotion (QL): four deceased and three living. The infantile hypotonia in the surviving cases gradually disappeared over a period of years, so that they could sit by about 10 years, crawl on hands and knees by about 12 years. They began walking on all fours around 14 years, habitually using QL. Neurological examinations showed normal tonus in their arms and legs, no Babinski sign, brisk tendon reflexes especially in the legs, and mild tremor. The patients could not walk in a straight line, but (except in one case) could stand up and maintain upright posture with truncal ataxia. Cerebello-vermial hypoplasia and mild gyral simplification were noted in their MRIs. The results of the genetic analysis were inconclusive: no genetic code could be identified as the triggering factor for the syndrome in these families. Instead, the extremely low socio-economic status of the patients was thought to play a role in the emergence of UTS, possibly by epigenetically changing the brain structure and function, with a consequent selection of ancestral neural networks for QL during locomotor development. It was suggested that UTS may be regarded as one of the unpredictable outcomes of self-organization within a complex system. It was also noted that the prominent feature of this syndrome, the diagonal-sequence habitual QL, generated an interference between ipsilateral hands and feet, as in non-human primates. It was suggested that this may have been the triggering factor for the attractor state “bipedal locomotion” (BL), which had visual and manual benefits for our ape-like ancestors, and therefore enhancing their chances for survival, with consequent developments in the psychomotor domain of humans. This was put forward as a novel theory of the evolution of BL in human beings.

Cerebellar dysfunction is closely related to cognitive decline in Uner Tan syndrome

Cerebellar dysfunction is closely related to cognitive decline in Uner Tan syndrome

Central Pattern Generator for Locomotion: Anatomical, Physiological, and Pathophysiological Considerations

This article provides a perspective on major innovations over the past century in research on the spinal cord and, specifically, on specialized spinal circuits involved in the control of rhythmic locomotor pattern generation and modulation. Pioneers such as Charles Sherrington and Thomas Graham Brown have conducted experiments in the early twentieth century that changed our views of the neural control of locomotion. Their seminal work supported subsequently by several decades of evidence has led to the conclusion that walking, flying, and swimming are largely controlled by a network of spinal neurons generally referred to as the central pattern generator (CPG) for locomotion. It has been subsequently demonstrated across all vertebrate species examined, from lampreys to humans, that this CPG is capable, under some conditions, to self-produce, even in absence of descending or peripheral inputs, basic rhythmic, and coordinated locomotor movements. Recent evidence suggests, in turn, that plasticity changes of some CPG elements may contribute to the development of specific pathophysiological conditions associated with impaired locomotion or spontaneous locomotor-like movements. This article constitutes a comprehensive review summarizing key findings on the CPG as well as on its potential role in Restless Leg Syndrome, Periodic Leg Movement, and Alternating Leg Muscle Activation. Special attention will be paid to the role of the CPG in a recently identified, and uniquely different neurological disorder, called the Uner Tan Syndrome.

An unusual neurological syndrome of crawling gait, dystonia, pyramidal signs, and limited speech

The purpose of the study was to identify and molecularly characterize a neurological syndrome in a consanguineous Pakistani family. Five patients, their 2 siblings, and their parents were clinically examined. DNA from all 7 siblings was genotyped with Affymetrix SNP arrays and sequencing of selected candidate genes. An unusual neurological syndrome of crawling gait, predominant leg dystonia, pyramidal signs, microcephaly, and suspected deafness segregated in the family. Three patients ambulated on hands and knees, either by hopping and crossing their legs, or by dragging the legs behind them. Two patients have acquired the ability to walk bipedally with a dystonic gait. Unexpectedly, no chromosomal region was homozygous in patients only. Under different disease models, we localized 7 chromosomal regions in the genome common to all patients. No pathogenic mutations were identified in selected candidate genes or the mitochondrial genome. We describe an unusual movement disorder syndrome reminiscent of but distinct from Uner Tan syndrome.

Uner Tan Syndrome: History, Clinical Evaluations, Genetics, and the Dynamics of Human Quadrupedalism

This review includes for the first time a dynamical systems analysis of human quadrupedalism in Uner Tan syndrome, which is characterized by habitual quadrupedalism, impaired intelligence, and rudimentary speech. The first family was discovered in a small village near Iskenderun, and families were later found in Adana and two other small villages near Gaziantep and Canakkale. In all the affected individuals dynamic balance was impaired during upright walking, and they habitually preferred walking on all four extremities. MRI scans showed inferior cerebellovermian hypoplasia with slightly simplified cerebral gyri in three of the families, but appeared normal in the fourth. PET scans showed a decreased glucose metabolic activity in the cerebellum, vermis and, to a lesser extent the cerebral cortex, except for one patient, whose MRI scan also appeared to be normal. All four families had consanguineous marriages in their pedigrees, suggesting autosomal recessive transmission. The syndrome was genetically heterogeneous. Since the initial discoveries more cases have been found, and these exhibit facultative quadrupedal locomotion, and in one case, late childhood onset. It has been suggested that the human quadrupedalism may, at least, be a phenotypic example of reverse evolution. From the viewpoint of dynamic systems theory, it was concluded there may not be a single factor that predetermines human quadrupedalism in Uner Tan syndrome, but that it may involve self-organization, brain plasticity, and rewiring, from the many decentralized and local interactions among neuronal, genetic, and environmental subsystems.

A new case of Uner Tan syndrome-With late childhood quadrupedalism

A new case of Uner Tan syndrome-With late childhood quadrupedalism

In restless legs syndrome, the neural substrates of the sensorimotor symptoms are also normally involved in upright standing posture and biped walking

Restless legs syndrome (RLS) exhibits sensorimotor symptoms. In familial cases, a gene at chromosomal location 9p-24-22 is linked to RLS and the expressed mutation is Dopamine Receptor Specific Individual Sensitivity (DRSIS). The symptoms are triggered during changes in alertness, generally at sleep hours, resulting from insufficient dopamine transmission. The conscious experience of sensory abnormalities are described as 'an urge to move the limbs with or without paresthesias' leading to motor signs such as periodic limb movements and motor restlessness which exhibit temporary loss of extensor motor system dominance over the flexor motor system of the upright posture. The relationship of the expressed mutation to EEG alpha activity makes RLS a sleep disorder as well as a cognitive dysfunction. The recurrent character of sensorimotor symptoms impede the patient's ability to sleep, wake and force to move leading to insomnia. In Uner Tan Syndrome, the nonsense mutation in the same gene leads to underdevelopment of the neural substrates of upright posture. The defects include dopamine receptor deficiency (DRD) leading to severe cognitive dysfunctions and motor disorders-complete loss of extensor motor system dominance over the flexor motor system-quadrupedality, primitive speech, cerebellar symptoms, and strabismus. Comparisons between the neural substrates of sensorimotor symptoms seen in RLS and MRI findings for cases of Uner Tan Syndrome show cortico-cerebellar hypoplasias in the neural networks involved in upright posture. Both RLS and Uner Tan Syndrome seem to be due to different mutations in the dopamine receptor gene at 9p-24 locus, affecting the diencephalon dopaminergic system and the neural networks involved in upright posture.

Unertan Syndrome: A New Variant of Unertan Syndrome: Running on All Fours in Two Upright-Walking Children

A new variant of Unertan Syndrome (UTS) is described in two Turkish children who exhibit both bipedal and quadrupedal locomotion and have normal cognitive abilities, including speech and intelligence. Quadrupedal locomotion was used by these individuals for rapid motivity when needed. An X-linked autosomal recessive transmission appears to be responsible for the UTS trait, with no intrafamilial marriages. The children did not show any neurological signs and symptoms except for a positive Babinski sign and an inability to perform a tandem walk. The results suggest that quadrupedality may result from using ancestral neural networks when needed. The preference for the quadrupedal gait as a hidden skill may be an example of learned dynamical adaptation to limited motor control, pointing out a phase transition in system dynamical terms. Human quadrupedality may have important consequences regarding human evolution with respect to the transition from quadrupedalism to bipedalism, which is generally recognized as important trait in the hominization process during human evolution.

“Devolution” of bipedality

Ozcelik et al. (1) report mutations in very-low-density lipoprotein receptor (VLDLR) that are associated with quadrupedal gait. They propose a pivotal role for VLDLR in the transition from quadrupedal to bipedal locomotion in man. VLDLR is a key regulator of cerebellar development in vertebrates (2). All VLDLR mutations reported to date result in disequilibirium syndrome (DES) with cerebellar hypoplasia and are neuroanatomically indistinguishable (1, 3, 4). In contrast to the Turkish population reported by Ozcelik et al., Hutterites carrying a complete deletion of VLDLR are bipedal (3). Ozcelik et al. hypothesize that the Hutterites are more severely afflicted because of a chromosomal deletion and that this causes loss of motor skills required for quadrupedal locomotion, thereby forcing them to habitually walk upright. Quadrupedal locomotion in individuals with cerebellar hypoplasia has been proposed to define a distinct genetic syndrome of “human devolution” or “reverse evolution” (“Unertan syndrome”) (5).

Discovery of Unertan Syndrome and Reverse Evolution: As An “Aha!” Experience.

For over 45 years I have been working on the motor system of cats (1960-1980) and humans (1980-2008) (My Scientific Odyssey in Tan, 2004). My favorite motor system has always been the extensor motor system, responsible for upright posture. My scientific work has concerned the motor system since 1960, especially the extensor muscles in relation to the human mind, on both philosophical and experimental grounds. My own mind has been continually scanning these topics, day and night. In fact, the aim of all of my scientific endeavors has been directed toward understanding man.

Mutations in the very low-density lipoprotein receptor VLDLR cause cerebellar hypoplasia and quadrupedal locomotion in humans.

Quadrupedal gait in humans, also known as Unertan syndrome, is a rare phenotype associated with dysarthric speech, mental retardation, and varying degrees of cerebrocerebellar hypoplasia. Four large consanguineous kindreds from Turkey manifest this phenotype. In two families (A and D), shared homozygosity among affected relatives mapped the trait to a 1.3-Mb region of chromosome 9p24. This genomic region includes the VLDLR gene, which encodes the very low-density lipoprotein receptor, a component of the reelin signaling pathway involved in neuroblast migration in the cerebral cortex and cerebellum. Sequence analysis of VLDLR revealed nonsense mutation R257X in family A and single-nucleotide deletion c2339delT in family D. Both these mutations are predicted to lead to truncated proteins lacking transmembrane and signaling domains. In two other families (B and C), the phenotype is not linked to chromosome 9p. Our data indicate that mutations in VLDLR impair cerebrocerebellar function, conferring in these families a dramatic influence on gait, and that hereditary disorders associated with quadrupedal gait in humans are genetically heterogeneous.