Novel KIAA0753 mutations extend the phenotype of skeletal ciliopathies.

The skeletal ciliopathies are a heterogeneous group of disorders with a significant clinical and genetic variability and the main clinical features are thoracic hypoplasia and short tubular bones. To date, 25 genes have been identified in association with skeletal ciliopathies. Mutations in the KIAA0753 gene have recently been associated with Joubert syndrome (JBTS) and orofaciodigital (OFD) syndrome. We report biallelic pathogenic variants in KIAA0753 in four patients with short-rib type skeletal dysplasia. The manifestations in our patients are variable and ranging from fetal lethal to viable and moderate skeletal dysplasia with narrow thorax and abnormal metaphyses. We demonstrate that KIAA0753 is expressed in normal fetal human growth plate and show that the affected fetus, with a compound heterozygous frameshift and a nonsense mutation in KIAA0753, has an abnormal proliferative zone and a broad hypertrophic zone. The importance of KIAA0753 for normal skeletal development is further confirmed by our findings that zebrafish embryos homozygous for a nonsense mutation in kiaa0753 display altered cartilage patterning.

Identification and characterization of 20 novel pathogenic variants in 60 unrelated Indian patients with mucopolysaccharidoses type I and type II.

Mucopolysaccharidoses (MPS), a subgroup of lysosomal storage disorders, are caused due to deficiency of specific lysosomal enzyme involved in catabolism of glycosaminoglycans. To date more than 200 pathogenic variants in the alpha-l-iduronidase (IDUA) for MPS I and ∼500 pathogenic variants in the iduronate-2-sulphatase (IDS) for MPS II have been reported worldwide. The mutation spectrum of MPS type I and MPS type II disorders in Indian population is not characterized yet. In this study, we carried out clinical, biochemical, molecular and in silico analyses to establish the mutation spectrum of MPS I and MPS II in the Indian population. We conducted molecular analysis for 60 MPS-affected patients [MPS I (n = 30) (Hurler syndrome = 17, Hurler-Scheie syndrome = 13), and MPS II (n = 30) (severe = 18, attenuated = 12)] and identified a total of 44 [MPS I (n = 22) and MPS II (n = 22)] different pathogenic variants comprising missense, nonsense, frameshift, gross deletions and splice site variants. A total of 20 [MPS I (n = 14), and MPS II (n = 6)] novel pathogenic sequence variants were identified in our patient cohort. We found that 32% of pathogenic variants detected in IDUA were recurrent and 25% in MPS II. This is the first study revealing the mutation spectrum of MPS I and MPS II patients in the Indian population.

Mutant B-RAF-Mcl-1 survival signaling depends on the STAT3 transcription factor.

Approximately 50% of melanomas depend on mutant B-RAF for proliferation, metastasis and survival. The inhibition of oncogenic B-RAF with highly targeted compounds has produced remarkable albeit short-lived clinical responses in B-RAF mutant melanoma patients. Reactivation of signaling downstream of B-RAF is frequently associated with acquired resistance to B-RAF inhibitors, and the identification of B-RAF targets may provide new strategies for managing melanoma. Oncogenic B-RAF(V600E) is known to promote the stabilizing phosphorylation of the anti-apoptotic protein Mcl-1, implicated in melanoma survival and chemoresistance. We now show that B-RAF(V600E) signaling also induces the transcription of Mcl-1 in melanocytes and melanoma. We demonstrate that activation of STAT3 serine-727 and tyrosine-705 phosphorylations is promoted by B-RAF(V600E) activity and that the Mcl-1 promoter is dependent on a STAT consensus-site for B-RAF-mediated activation. Consequently, suppression of STAT3 activity disrupted B-RAF(V600E)-mediated induction of Mcl-1 and reduced melanoma cell survival. We propose that STAT3 has a central role in the survival and contributes to chemoresistance of B-RAF(V600E) melanoma.

Crossed polydactyly and Greig cephalopolysyndactyly syndrome.

Greig cephalopolysyndactyly syndrome is a rare genetic disorder, with an autosomal dominant inheritance and consisting of a triad of polysyndactyly, macrocephaly and hypertelorism. Crossed polydactyly is a finding characteristically associated with this syndrome. We report a one and half year old male child who presented with classic clinical features and family history diagnostic of the above syndrome.

NRADD, a novel membrane protein with a death domain involved in mediating apoptosis in response to ER stress.

NRADD (neurotrophin receptor alike death domain protein) is a novel protein with transmembrane and cytoplasmic regions highly homologous to death receptors, particularly p75(NTR). However, the short N-terminal domain is unique. Expression of NRADD induced apoptosis in a number of cell lines. The apoptotic mechanism involved the activation of caspase-8 and execution of apoptosis without requiring mitochondrial components. The activation of this death receptor-like mechanism required the N-terminal domain, which is N-glycosylated and needed for subcellular targeting. Deletion of the N-terminal domain produced a dominant-negative form of NRADD that protected neurons and Schwann cells from a variety of endoplasmic reticulum (ER) stressors. NRADD may therefore be a necessary component for generating an ER-induced proapoptotic signal.

Disturbed CD4+ T cell homeostasis and in vitro HIV-1 susceptibility in transgenic mice expressing T cell line-tropic HIV-1 receptors.

T cell line-tropic (T-tropic) HIV type 1 strains enter cells by interacting with the cell-surface molecules CD4 and CXCR4. We have generated transgenic mice predominantly expressing human CD4 and CXCR4 on their CD4-positive T lymphocytes (CD4+ T cells). Their primary thymocytes are susceptible to T-tropic but not to macrophage-tropic HIV-1 infection in vitro, albeit with a viral antigen production less efficient than human peripheral blood mononuclear cells. Interestingly, even without HIV infection, transgenic mice display a CD4+ T cell depletion profile of peripheral blood reminiscent of that seen in AIDS patients. We demonstrate that CD4+ T cell trafficking in transgenic mice is biased toward bone marrow essentially due to CXCR4 overexpression, resulting in the severe loss of CD4+ T cells from circulating blood. Our data suggest that CXCR4 plays an important role in lymphocyte trafficking through tissues, especially between peripheral blood and bone marrow, participating in the regulation of lymphocyte homeostasis in these compartments. Based on these findings, we propose a hypothetical model in which the dual function of CXCR4 in HIV-1 infection and in lymphocyte trafficking may cooperatively induce progressive HIV-1 infection and CD4+ T cell decline in patients.

Varied manifestations of viral myocarditis.

Nine children in the age group of new born to 10 years were seen during the period October 1989 to January 1993 with varying manifestations of Myocarditis. This ranged from cardiogenic shock due to fulminant cardiac failure, recurrent wheezy episodes (mistakenly treated as bronchial asthma) bronchiolitis and rhythm disturbances. Clinical picture was collaborated by radiological evidence of cardiomegaly, ECG changes of low voltage QRS complexes with ST depression, T wave inversion or signs of left ventricular dilatation. SGOT, SGPT, CPK, LDH were elevated significantly in 7 cases. Echocardiographic changes ranged from left ventricular dilatation to global hypokinesia and mild mitral incompetence. Viral studies suggested infection with Coxsackie B1 in 4 cases, B4 in 2, B5 in 2 and Dengue 3 in 1 case. All the children recovered well with routine anti failure measures and treatment of arrhythmias and 2 children needed steroid therapy. At the end of follow up of 6 months to 1 year there has been complete reversal of ECHO changes to normal. Viral Myocarditis can manifest in varied ways in children and if treated adequately may lead to complete recovery.