X-linked mental retardation, short stature, microcephaly and hypogonadism maps to Xp22.1-p21.3 in a Belgian family

X-linked mental retardation (XLMR) is a heterogeneous disorder that can be classified as either non-specific (MRX), when mental retardation is the only feature, or as syndromic mental retardation (MRXS). Genetic defects underlying XLMR are being identified at a rapid pace, often starting from X-chromosomal aberrations and XLMR families with a well-defined linkage interval. Here, we present a new family with a syndromic form of XLMR, including mild mental retardation, short stature, microcephaly and hypogonadism. Two-point linkage analysis with 24 polymorphic markers spanning the entire X chromosome was carried out. We could assign the causative gene to a 6 cM interval in Xp22.1-p21.3, with a maximum LOD score of 2.61 for markers DXS989 and DXS1061 at theta = 0.00. No mutations were found in the presented family for two known MRX genes mapping to this interval, ARX and IL1RAPL-1. These data indicate that the interval Xp22.1-p21.3 contains at least one additional MRXS gene.     

Primary microcephaly,primordial dwarfism,and brachydactyly in adult cases with biallelic skipping of RTTN exon 42

Biallelic and pathogenic variants in the RTTN gene, encoding the centrosomal protein Rotatin, are associated with variable degrees of neurodevelopmental abnormalities, microcephaly, and extracranial malformations. To date, no reported case has reached their third decade. Herein, we report on a consanguineous family with three adult members, age 43, 57, and 60 years respectively, with primary microcephaly, developmental delay, primordial dwarfism, and brachydactyly segregating a homozygous splice site variant NM_173630.3:c.5648–5T>A in RTTN. The variant RTTN allele results in a nonhypomorphic skipping of exon 42 and a frameshift [(NP_775901.3:p.Ala1883Glyfs*6)]. Brain MRI of one affected individual showed markedly reduced volume of cerebral lobes and enlarged sulci but without signs of neural migration defects. Our assessment of three adult cases with a biallelic RTTN variant shows that a predicted shortened Rotatin, lacking the C‐terminal end, are associated with stationary clinical features into the seventh decade. Furthermore, our report adds brachydactyly to the phenotypic spectrum in this pleiotropic entity.     

Biallelic loss of function variants in ATP1A2 cause hydrops fetalis,microcephaly, arthrogryposis and extensive cortical malformations

The Na⁺/K⁺- ATPase acts as an ion pump maintaining the essential plasma membrane potential in all mammalian cell types, and is essential for many cellular functions. There are four α isoforms (α1, α2, α3 and α4) with distinct expression patterns, kinetic properties and substrate affinity. The α2-isoform is encoded by ATP1A2 and evidence supports its utmost importance in Cl⁻ homeostasis in neurons, and in the function of respiratory neurons at birth. Monallelic pathogenic variants in ATP1A2 are associated with familial hemiplegic migraine type 2 (FHM2) and on rare occasions with alternating hemiplegia of childhood 1 (AHC1). To date, no instances of biallelic loss of function variants have been reported in humans. However, Atp1a2 homozygous loss of function knockout mice (α2^−/− mice) show severe motor deficits, with lack of spontaneous movements, and are perinatally lethal due to absent respiratory activity. In this report we describe three newborns from two unrelated families, who died neonatally, presenting in utero with an unusual form of fetal hydrops, seizures and polyhydramnios. At birth they had multiple joint contractures (e.g. arthrogryposis), microcephaly, malformations of cortical development, dysmorphic features and severe respiratory insufficiency. Biallelic loss of function variants in ATP1A2, predicted to be pathogenic were found on whole exome sequencing. We propose that this is a distinctive new syndrome caused by complete absence of Na⁺/K⁺- ATPase α2-isoform expression.     

Tubulin genes and malformations of cortical development

A large number of genes encoding for tubulin proteins are expressed in the developing brain. Each is subject to specific spatial and temporal expression patterns. However, most are highly expressed in post-mitotic neurons during stages of neuronal migration and differentiation. The major tubulin subclasses (alpha- and beta-tubulin) share high sequence and structural homology. These globular proteins form heterodimers and subsequently co-assemble into microtubules. Microtubules are dynamic, cytoskeletal polymers which play key roles in cellular processes crucial for cortical development, including neuronal proliferation, migration and cortical laminar organisation. Mutations in seven genes encoding alpha-tubulin (TUBA1A), beta-tubulin (TUBB2A, TUBB2B, TUBB3, TUBB4A, TUBB) and gamma-tubulin (TUBG1) isoforms have been associated with a wide and overlapping range of brain malformations or “Tubulinopathies”. The majority of cortical phenotypes include lissencephaly, polymicrogyria, microlissencephaly and simplified gyration. Well-known hallmarks of the tubulinopathies include dysmorphism of the basal ganglia (fusion of the caudate nucleus and putamen with absence of the anterior limb of the internal capsule), midline commissural structures hypoplasia and/or agenesis (anterior commissure, corpus callosum and fornix), hypoplasia of the oculomotor and optic nerves, cerebellar hypoplasia or dysplasia and dysmorphism of the hind-brain structures. The cortical and extra-cortical brain phenotypes observed are largely dependent on the specific tubulin gene affected. In the present review, all the published data on tubulin family gene mutations and the associated cortical phenotypes are summarized. In addition, the most typical neuroimaging patterns of malformations of cortical development associated with tubulin gene mutations detected on the basis of our own experience are described.     

A new X-linked mental retardation (XLMR) syndrome with late-onset primary testicular failure, short stature and microcephaly maps to Xq25-q26

X-linked mental retardation (XLMR) is a heterogeneous disorder with both syndromic and non-syndromic forms. Here we describe the clinical and molecular characterisation of a family with a syndromic form of XLMR with hypogonadism and short stature. We investigated a family in which four male members in two generations presented with hypergonadotrophic hypogonadism associated with development of small and abnormal testes. In two of the males, late-onset testicular ascent was noted. In addition, all affected males had short stature (<0.4th centile) and mild learning difficulties and three out of the four had microcephaly. Karyotypes were normal and endocrine investigations confirmed primary testicular failure. The phenotype segregated as an X-linked trait. Haplotype and genetic two-point linkage analysis with 22 microsatellites excluded the whole X chromosome except for a region on Xq25-Xq27 encompassing 13.7Mb with a maximum LOD score of 1.1 for marker DXS8038 at theta=0.05. One family previously described as having XLMR with hypogonadism and short stature maps to the same X chromosome region implicated in our family. However, the more severe mental retardation, muscle wasting and tremor described in this other family would suggest that our family is affected by a novel XLMR syndrome.     

Cataracts, ataxia, short stature, and mental retardation in a Chinese family mapped to Xpter-q13.1

Six males in a Chinese family affected by congenital cataracts, cerebellar ataxia, short stature, and mental retardation, which were tentatively named CASM syndrome. Eight female carriers in the family had cataracts alone. Linkage analysis demonstrated that the disease is transmitted through X-linked inheritance, either by setting the syndrome in males as an X-linked recessive trait, or by setting cataracts in the family as an X-linked dominant trait. The gene responsible for the syndrome is mapped to Xpter-Xq13.1, with the highest lod score of 3.91 for DXS1226, DXS991, and DXS1213 at θ = 0. Haplotype analysis identified that the allele harboring the disease gene co-segregated with all female carriers as well as affected males in the family. Clinically and genetically, the disease in this family is different from any known disease. Major features of CASM syndrome that distinguish it from other diseases are X-linked inheritance and cataracts in carrier females.Xiangming Guo, Huangxuan Shen, Xueshan Xiao, Qilin Dai, Fielding Hejtmancik, and Qingjiong Zhang contributed equally to this work     

Biallelic PRMT7 pathogenic variants are associated with a recognizable syndromic neurodevelopmental disorder with short stature,obesity, and craniofacial and digital abnormalities

PurposeProtein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyzes the methylation of arginine residues on several protein substrates. Biallelic pathogenic PRMT7 variants have previously been associated with a syndromic neurodevelopmental disorder characterized by short stature, brachydactyly, intellectual developmental disability, and seizures. To our knowledge, no comprehensive study describes the detailed clinical characteristics of this syndrome. Thus, we aim to delineate the phenotypic spectrum of PRMT7-related disorder.MethodsWe assembled a cohort of 51 affected individuals from 39 different families, gathering clinical information from 36 newly described affected individuals and reviewing data of 15 individuals from the literature.ResultsThe main clinical characteristics of the PRMT7-related syndrome are short stature, mild to severe developmental delay/intellectual disability, hypotonia, brachydactyly, and distinct facial morphology, including bifrontal narrowing, prominent supraorbital ridges, sparse eyebrows, short nose with full/broad nasal tip, thin upper lip, full and everted lower lip, and a prominent or squared-off jaw. Additional variable findings include seizures, obesity, nonspecific magnetic resonance imaging abnormalities, eye abnormalities (i.e., strabismus or nystagmus), and hearing loss.ConclusionThis study further delineates and expands the molecular, phenotypic spectrum and natural history of PRMT7-related syndrome characterized by a neurodevelopmental disorder with skeletal, growth, and endocrine abnormalities.     

A de novo 7.6Mb tandem duplication of 14q32.2-qter associated with primordial short stature with neurosecretory growth hormone dysfunction, distinct facial anomalies and mild developmental delay

We delineate a pure "distal 14q duplication" phenotype, characterized by primordial short stature, mild developmental delay, and distinct facial dysmorphism with high forehead, mild hypertelorism, broad nasal bridge, dysplastic ear helices, short philtrum, thin and "cupid bow" upper lip, broad mouth, and micrognathia.     

Distal aphalangia,syndactyly, and extra metatarsal,associated with short stature,microcephaly, and borderline intelligence: A new autosomal dominant disorder

We report on 3 members of a Spanish family with partial aphalangia, syndactyly with duplication of metatarsal IV, microcephaly, dull intelligence, and short stature. The MCA pattern observed in this family appears to constitute a previously underscribed syndrome. © 1995 Wiley-Liss, Inc.     

Allelic variations of the D2 dopamine receptor gene in children with idiopathic short stature

The D2 dopamine receptor (DRD2) plays a major role in growth hormone (GH) secretion. Recent reports indicate that Taq I A DRD2 gene alleles (A1 and A2) are related to the function of DRD2. Idiopathic short stature (ISS) is defined as short stature without accompanying malnutrition, chronic disease, and endocrinological disorders. However, some reports suggest that ISS is associated with a mild disturbance of GH secretion. In this study, we examined the notion that allelic variants of the DRD2 are associated with ISS. We studied 55 children with ISS aged 8.4 (SD 2.9) years; (group I) and 104 age-matched children of normal stature (group II). Informed consent was obtained from each child's parent or guardian. Genomic DNAs were extracted from peripheral mononuclear cells and amplified by polymerase chain reaction (PCR). The PCR products were digested by Taq1 and resolved by electrophoresis. The frequency of the A1 allele was significantly higher in group I (0.42) than in group II (0.26). The insulin-like growth factor (IGF)-I ratio (the ratio of the individual level to the normal mean value according to age at our laboratory center) was significantly lower in group I than in group II. When group I was subdivided into group A (with the A1 allele) and group B (with only the A2 allele), group A had a significantly lower peak GH response to the l-dopa test, lower levels of IGF-I, and retarded bone maturation. These findings indicate that polymorphism of the DRD2 gene may be one genetic factor that affects body height in childhood, acting through the hypothalamus (GH-releasing hormone) — pituitary (GH) — IGF-I axis. Received: July 13, 1998 / Accepted: September 9, 1998     

Expanding the phenotype of RTTN variations: a new family with primary microcephaly,severe growth failure,brain malformations and dermatitis

Primary autosomal recessive microcephaly (MCPH) is a developmental disorder characterized by prenatal onset of abnormal brain growth. MCPH occurs both alone and as part of a broad range of neurodevelopmental syndromes with or without cortical malformations and growth retardation. Here we report a consanguineous Moroccan family with two siblings affected by severe primary microcephaly, failure to thrive, congenital dermatitis and severe developmental delay. Brain magnetic resonance imaging showed lissencephaly of frontal lobes and periventricular heterotopia of the gray matter. We performed both Comparative Genomic Hybridization array and whole exome sequencing (WES) analyses of the kindred. No quantitative defects were detected. However, WES identified a new homozygous missense variation in the penultimate nucleotide of exon 23 of RTTN gene (c.2953A>G;pArg985Gly). cDNA sequencing revealed two abnormal spliced products, one lacking only exon 23 and the other lacking exons 22 and 23 (out‐of‐frame). RTTN is a protein involved in cilia structure and function. Homozygous mutations in RTTN gene have been described in bilateral diffuse isolated polymicrogyria and, more recently, in microcephalic primordial dwarfism (PD). We found a novel homozygous mutation in RTTN associated with microcephalic PD as well as complex brain malformations and congenital dermatitis, thus expanding the phenotypic spectrum of both RTTN‐associated diseases and ciliary dysfunction.     

Multigeneration family with short stature,developmental delay,and dysmorphic features due to 4q27-q28.1 microdeletion

Deletions of the long arm of chromosome 4 are rare but have been previously reported to be associated with craniofacial anomalies, digital anomalies, developmental delay, growth failure, and cardiovascular anomalies [1], [2], [3], [4], [5], [6]. Strehle et al. [1] previously presented 20 patients with 4q deletions and began to construct a phenotype–genotype map for chromosome 4q. This report follows up on that work by providing clinical and molecular cytogenetic data on a three generation pedigree including seven patients with short stature, dysmorphic features, and developmental delay identified to have a 4q27-q28.1 microdeletion of approximately 5.68 Mb by oligonucleotide chromosomal microarray. This family represents a rare report of an inherited interstitial deletion of the long arm of chromosome 4. To our knowledge, only two cases have been previously reported [7], [8]. The contribution of candidate genes in the region is discussed.     

An apparent new syndrome of extreme short stature,microcephaly, dysmorphic faces,intellectual disability,and a bone dysplasia of unknown etiology

We report on a 26‐year‐old male with extreme short stature, microcephaly, macroglossia, other dysmorphic features, severe intellectual disability, and a bone dysplasia. The patient had an extensive genetic and biochemical evaluation that was all normal or noninformative. Recently, the proband died following a period of not eating. He likely had a previously undescribed syndrome of unknown etiology.     

基因重组人生长激素治疗特发性身材矮小儿童的临床观察

目的为了了解基因重组人生长激素(r-hGH)治疗特发性身材矮小儿童时其对身高、青春期的影响.方法我们对14例特发性身材矮小(ISS)儿童采用r-hGH治疗3～12月,比较其治疗前后的年生长速率和青春发育情况.结果经r-hGH治疗,特发性身材矮小儿童的年生长速率有显著提高,身高年龄的增长明显快于生活年龄和骨龄的增长,但没有明显青春期加速的现象.结论r-hGH可显著改善特发性身材矮小儿童的身高,且青春期、骨龄均不提前.     

Microdeletion at 4q21.3 is associated with intellectual disability, dysmorphic facies, hypotonia, and short stature

Chromosomal imbalances are a major cause of intellectual disability (ID) and multiple congenital anomalies. We have clinically and molecularly characterized two patients with chromosome translocations and ID. Using whole genome array CGH analysis, we identified a microdeletion involving 4q21.3, unrelated to the translocations in both patients. We confirmed the 4q21.3 microdeletions using fluorescence in situ hybridization and quantitative genomic PCR. The corresponding deletion boundaries in the patients were further mapped and compared to previously reported 4q21 deletions and the associated clinical features. We determined a common region of deletion overlap that appears unique to ID, short stature, hypotonia, and dysmorphic facial features.     

Drayer's syndrome of mental retardation, microcephaly, short stature and absent phalanges is caused by a recurrent deletion of chromosome 15(q26.2-->qter)

We reevaluated a unique family with two sibs who had a presumed autosomal recessively inherited syndrome characterized by mental retardation, microcephaly, short stature and absent phalanges. This family was originally described by Drayer et al. in 1977. Using modern molecular techniques, we demonstrated that the syndrome is caused by the recurrence of an apparently de novo 15qter deletion of 5.8 Mb. Analysis of polymorphic markers revealed that the deletion was of maternal origin in both cases, indicating germline mosaicism in the clinically unaffected mother. This study demonstrates the possibility of parental mosaicism and the risk of recurrence in sibs for terminal subtelomeric deletions.     

上海市城郊两区整群抽样6～18岁儿童青少年身高分布特点及矮小症患病率调查

目的研究上海市6～18岁儿童青少年身高及矮小症患病率分布特点。方法采用整群抽样抽取上海市1个城区和1个郊区,普查2个区内所有6～18岁共70431名中小学生的身高。分析身高的年龄别分布特点,并与1975、1995年全国和上海市学生体质测试标准进行比较;并以1995年上海市身高评价标准进行评价,分析矮小症患病率分布特点。结果①研究人群中身高特点为男性显著高于女性（P〈0．0001）。②男性身高增长以6-15岁较为明显,11岁后身高增长加快,15岁后增幅减小;女性身高增长在6—14岁较为明显,10岁以后增长加快,14岁后增幅减小。③与全国身高标准相比,上海城区和郊区儿童青少年的各年龄组身高均高于全国标准。与1975年上海儿童青少年身高参考标准相比,身高增长分别为城区男性（6．4±2．1）cm,郊区男性（10．5±2．5）cm,城区女性（4．8±0．9）cm,郊区女性（8．6±1．9）cm,其中以郊区儿童青少年特别是11岁以上儿童青少年身高增长更为显著;而城区儿童青少年身高在1995至2003年的增幅较小,在1975至1995年增幅较大：④上海市儿童青少年各年龄组总体矮小症的患病率为0．5％～6．03％,平均患病率为3．77％;城区矮小症的粗患病率为2．78％,标准化患病率为2．57％;郊区矮小症的粗患病率为4．52％,标准化患病率为3．75％。矮小症患病率在13岁以前较高;城区矮小症患病率低于郊区,男、女矮小症患病率在城区相近,在郊区则男性高于女性。结论上海市儿童青少年身高生长曲线存在性别的三相性差异,6～9岁和12～18岁均呈现男高女低,10—11岁呈现女高男低的特点。1975至2003年上海儿童青少年身高均呈现显著增长现象,但城区儿童身高在1995年后增幅明显减小。上海儿童青少年平均矮小症患病率为3．77％,患病率在13岁以前较高;郊区儿童青少年矮小症患病率高于城区。