Mendelian Inheritance in Man

Although clinical features in Turner syndrome have been well defined, underlying genetic factors have not been clarified. To deduce the factors leading to the development of clinical features, we took the following four steps: (1) assessment of clinical features in classic 45,X Turner syndrome; (2) review of clinical features in various female sex chromosome aberrations (karyotype-phenotype correlations); (3) assessment of factors that could lead to Turner features; and (4) correlation of the clinical features with the effects of specific factors. The results indicate that the clinical features in 45,X and in other female sex chromosome aberrations may primarily be determined by: (1) degree of global non-specific developmental defects caused by quantitative alteration of a euchromatic or noninactivated region; (2) dosage effect of a pseudoautosomal growth gene(s), a Y-specific growth gene(s), and an Xp-Yp homologous lymphogenic gene(s); and (3) degree of chromosome pairing failure in meiocytes that are destined to develop as oocytes in the absence of SRY.

Turner syndrome and female sex chromosome aberrations: deduction of the principal factors involved in the development of clinical features.

The transcription factor Sox9 was first discovered in patients with campomelic dysplasia, a haploinsufficiency disorder with skeletal deformities caused by dysregulation of Sox9 expression during chondrogenesis. Since then, its role as a cell fate determiner during embryonic development has been well characterized; Sox9 expression differentiates cells derived from all three germ layers into a large variety of specialized tissues and organs. However, recent data has shown that ectoderm- and endoderm-derived tissues continue to express Sox9 in mature organs and stem cell pools, suggesting its role in cell maintenance and specification during adult life. The versatility of Sox9 may be explained by a combination of post-transcriptional modifications, binding partners, and the tissue type in which it is expressed. Considering its importance during both development and adult life, it follows that dysregulation of Sox9 has been implicated in various congenital and acquired diseases, including fibrosis and cancer. This review provides a summary of the various roles of Sox9 in cell fate specification, stem cell biology, and related human diseases. Ultimately, understanding the mechanisms that regulate Sox9 will be crucial for developing effective therapies to treat disease caused by stem cell dysregulation or even reverse organ damage.

The versatile functions of Sox9 in development, stem cells, and human diseases.

Congenital colobomata of the eye are important causes of childhood visual impairment and blindness. Ocular coloboma can be seen in isolation and in an impressive number of multisystem syndromes, where the eye phenotype is often seen in association with severe neurological or craniofacial anomalies or other systemic developmental defects. Several studies have shown that, in addition to inheritance, environmental influences may be causative factors. Through work to identify genes underlying inherited coloboma, significant inroads are being made into understanding the molecular events controlling closure of the optic fissure. In general, severity of disease can be linked to the temporal expression of the gene, but this is modified by factors such as tissue specificity of gene expression and genetic redundancy.

https://jmg.bmj.com/content/jmedgenet/41/12/881.full.pdf

Ocular coloboma: a reassessment in the age of molecular neuroscience

Since the group of disorders known as the distal arthrogryposes (DAs) were defined, additional disorders characterized by multiple congenital contractures of the distal limbs were described, and the distribution of phenotypic findings in the DAs has been expanded. The breadth of disorders labeled as DAs has diminished the usefulness of the DA classification. We propose a strict definition of DA and diagnostic criteria for DA disorders. Subsequently, we use these standards and propose a revised classification of discrete conditions that should be labeled DAs. Optimally, this serves as a framework for a DA classification based on underlying molecular and physiologic abnormalities.

A revised and extended classification of the distal arthrogryposes

Hypertrichosis is a rare condition characterized by excessive growth of hair (terminal, vellus or lanugo) in areas of the body that are not predominantly androgen dependent, and it is independent of age, race or sex. It can be congenital, late‐onset, generalized, localized, inherited or acquired. More than 50 different OMIM entries related to hypertrichosis exist, few of them with a localized gene locus or with a candidate gene. The review of generalized hypertrichoses from a historical point of view, including a review of their clinical and genetic features, shows heterogeneity with at least nine different entities. A short analysis of other forms of hypertrichosis is presented.

Inherited hypertrichoses: Inherited hypertrichoses

We describe four members of a family in which the clinical and radiological findings lead to consider the diagnosis of osteopoikilosis. The symptoms in all affected members were only those referred to as typical radiological features; these features became more extensive with older age. None of the subjects showed the skin lesions reported in the Buschke-Ollendorff syndrome. The importance of a suitable differential diagnosis is emphasized in order to avoid dangerous and unnecessary treatments.

Osteopoikilosis : report of a familial case

Garcia-Cruz D, Figuera LE, Feria-Velazco A, Sanchez-Corona J, Garcia-Cruz MO, Ramirez-Duenas RM, Hernandez-Cordova A, Ruiz MX, Bitar-Alatorre WE, Ramirez-Duenas ML, Cantu JM. The Myhre syndrome: report of two cases.



Clin Genet 1993: 44: 203–207. © Munksgaard, 1993



Two unrelated patients, aged 19 and 6 years, were studied and diagnosed as having Myhre syndrome (MS). This review, together with three previous cases, permits further delineation of MS. The main features are: short stature, mental retardation, blepharophimosis, muscular hypertrophy, decreased joint mobility, thick calvarium, broad ribs, hypoplastic iliac wings and short tubular bones. Advanced paternal age at the propositi's birth suggests an autosomal dominant mutation as the cause of MS.

The Myhre syndrome: report of two cases.

Two sisters, aged 18 and 11 years, were found to have an intrauterine growth retardation-malformation syndrome which included camptodactyly as a typical sign. The overall analysis of the clinical and radiological findings permitted the individualization of a distinct entity. The family data suggested autosomal recessive inheritance.

Guadalajara camptodactyly syndrome. A distinct probably autosomal recessive disorder.

A girl aged 13 years and 9 months with a phenotypic appearance of 9p trisomy was studied. Chromosome analysis of peripheral blood lymphocytes revealed a 9p tetrasomy [47,XX,+i(9p)] with no evidence of mosaicism. Biochemical studies corroborate the gene dosage effect for galactose-1-phosphate uridyltransferase. The roentgenological findings were quite similar to those of the 9p trisomy except for hypoplastic and angulated ribs, and malformed vertebral bodies, which are probably exclusive of the tetrasomic state.

Diana García-Cruz

Papers

Inherited hypertrichoses: Inherited hypertrichoses

Osteopoikilosis : report of a familial case

The Myhre syndrome: report of two cases.

Guadalajara camptodactyly syndrome. A distinct probably autosomal recessive disorder.

Tetrasomy 9p: clinical aspects and enzymatic gene dosage expression.