APCDD1 is a novel Wnt inhibitor mutated in hereditary hypotrichosis simplex

Methylation of cancer-stem-cell-associated Wnt target genes predicts poor prognosis in colorectal cancer patients

Gene signatures derived from cancer stem cells (CSCs) predict tumor recurrence for many forms of cancer. Here, we derived a gene signature for colorectal CSCs defined by high Wnt signaling activity, which in agreement with previous observations predicts poor prognosis. Surprisingly, however, we found that elevated expression of Wnt targets was actually associated with good prognosis, while patient tumors with low expression of Wnt target genes segregated with immature stem cell signatures. We discovered that several Wnt target genes, including ASCL2 and LGR5, become silenced by CpG island methylation during progression of tumorigenesis, and that their re-expression was associated with reduced tumor growth. Taken together, our data show that promoter methylation of Wnt target genes is a strong predictor for recurrence of colorectal cancer, and suggest that CSC gene signatures, rather than reflecting CSC numbers, may reflect differentiation status of the malignant tissue.

Dynamic signals for hair follicle development and regeneration

Hair follicles form during embryonic development and, after birth, undergo recurrent cycling of growth, regression, and relative quiescence. As a functional mini-organ, the hair follicle develops in an environment with dynamic and alternating changes of diverse molecular signals. Over the past decades, genetically engineered mouse models have been used to study hair follicle morphogenesis and significant advances have been made toward the identification of key signaling pathways and the regulatory genes involved. In contrast, much less is understood in signals regulating hair follicle regeneration. Like hair follicle development, hair follicle regeneration probably relies on populations of stem cells that undergo a highly coordinated and stepwise program of differentiation to produce the completed structure. Here, we review recent advances in the understanding of the molecular signals underlying hair follicle morphogenesis and regeneration, with a focus on the initiation of the primary hair follicle structure placode. Knowledge about hair follicle morphogenesis may help develop novel therapeutic strategies to enhance cutaneous regeneration and improve wound healing.

Hepatocyte growth factor is crucial for development of the carapace in turtles

Turtles are characterized by their shell, composed of a dorsal carapace and a ventral plastron. The carapace first appears as the turtle-specific carapacial ridge (CR) on the lateral aspect of the embryonic flank. Accompanying the acquisition of the shell, unlike in other amniotes, hypaxial muscles in turtle embryos appear as thin threads of fibrous tissue. To understand carapacial evolution from the perspective of muscle development, we compared the development of the muscle plate, the anlage of hypaxial muscles, between the Chinese soft-shelled turtle, Pelodiscus sinensis, and chicken embryos. We found that the ventrolateral lip (VLL) of the thoracic dermomyotome of P. sinensis delaminates early and produces sparse muscle plate in the lateral body wall. Expression patterns of the regulatory genes for myotome differentiation, such as Myf5, myogenin, Pax3, and Pax7 have been conserved among amniotes, including turtles. However, in P. sinensis embryos, the gene hepatocyte growth factor (HGF), encoding a regulatory factor for delamination of the dermomyotomal VLL, was uniquely expressed in sclerotome and the lateral body wall at the interlimb level. Implantation of COS-7 cells expressing a HGF antagonist into the turtle embryo inhibited CR formation. We conclude that the de novo expression of HGF in the turtle mesoderm would have played an innovative role resulting in the acquisition of the turtle-specific body plan.

Physiological inhibitors of Wnt signaling

Wnt signaling is crucial for cell proliferation and differentiation. It represents a complex network with mechanisms of self-regulation through positive and negative feedback. Recent increasing interest in this signaling pathway has led to the discovery of many new proteins that down-regulate Wnt activity. Here, we provide a short description of the most important and best-studied inhibitors, group them according to the target molecule within the Wnt cascade, and discuss their clinical potential. Although most of the inhibitors discussed here may also interact with proteins from other signaling pathways, we focus only on their ability to modulate Wnt signaling.

Impact of WNT signaling on tissue lineage differentiation in the early mouse embryo

WNT signaling activity is involved in the regulation of many cellular functions, including proliferation, migration, cell fate specification, maintenance of pluripotency and induction of tumorigenicity. Here we summarize recent progress towards understanding the regulation of canonical WNT/β-catenin signaling activity through feedback regulatory loops involving the ligands, agonists and antagonists, the availability of intracellular pools of active β-catenin and the cross-regulation of the WNT activity by β-catenin independent pathway. We also review recent findings on the role of WNT/β-catenin signaling in tissue lineage differentiation during embryogenesis and the maintenance and self renewal of embryo-derived stem cells in vitro.

Mutation in ribosomal protein L21 underlies hereditary hypotrichosis simplex

Hereditary hypotrichosis simplex (HHS) is a form of nonsyndromic inherited hair loss disorders without characteristic hair shaft changes, which has marked genetic and clinical heterogeneity. After mapping the locus to 13q12.12-12.3 in a Chinese family with a generalized variant of autosomal dominant HHS (ADHHS), exome sequencing was performed in an affected individual. The cause of the disease in this family was identified as a c.95G>A (p.Arg32Gln) mutation in the RPL21 gene, which encoding the ribosomal protein L21. This mutation cosegregated completely with the disease phenotype and was not observed in unaffected family members, 200 normal controls, the dbSNP database, the YH database or pilot data from the 1000 Genomes Project. Additionally, this mutation was found in two patients from another unrelated Chinese family with HHS. To the best of our knowledge, this is the first report describing the involvement of a ribosomal protein gene mutation in a non-syndromic hair loss disorder.

Novel mutations in the keratin-74 (KRT74) gene underlie autosomal dominant woolly hair/hypotrichosis in Pakistani families

Autosomal dominant woolly hair (ADWH) is an inherited condition of tightly curled and twisted scalp hair. Recently, a mutation in human keratin-74 (KRT74) gene has been shown to cause this form of hereditary hair disorder. In the present study, we have described two families (A and B) having multiple individuals affected with autosomal dominant form of hair loss disorders. In family A, 10 individuals showed ADWH phenotype while in the family B, 14 individuals showed hypotrichosis of the scalp. Genotyping using polymorphic microsatellite markers showed linkage of both the families to type II keratin gene cluster on the chromosome 12q12-14.1. Mutation analysis of the KRT74 gene identified two novel mutations in the affected individuals of the families. The sequence analysis revealed a splice acceptor site mutation (c.IVS8-1G>A) in family A and a missense variant (c.1444G>A, p.Asp482Asn) in family B. Mutations identified in the present study extend the body of evidence implicating the KRT74 gene in the pathogenesis of autosomal dominant hair loss disorders.

A novel mutation in LPAR6 causes autosomal recessive hypotrichosis of the scalp

BACKGROUND

Autosomal recessive hypotrichosis simplex (ARHS) presents with progressive hair loss mainly affecting the scalp area. In a small number of families, the condition has been associated with mutations in three distinct genes: DSG4, LIPH and LPAR6.

AIM

To identify the molecular basis of ARHS in a consanguineous family of Turkish extraction.

METHODS

We used a combination of microsatellite marker screening and direct sequencing.

RESULTS

We identified a novel missense mutation (c.C587T) in the human LPAR6 gene, resulting in the amino acid substitution p.P196L. The mutation affects a highly conserved amino acid residue, and is predicted to disrupt signalling through the P2Y5 receptor.

CONCLUSIONS

This study provides further evidence supporting a role for the lysophosphatidyl signalling pathway in hair growth and differentiation. In addition, this paper reports, for the first time to our knowledge, the use of homozygosity mapping as a premutation screening tool in the diagnosis of a group of inherited hair disorders.

Wnt/beta-catenin signaling in T-cell immunity and cancer immunotherapy

Wnt ligands are lipid-modified secreted glycoproteins that regulate embryonic development, cell fate specification, and the homeostasis of self-renewing adult tissues. In addition to its well-established role in thymocyte development, recent studies have indicated that Wnt/β-catenin signaling is critical for the differentiation, polarization, and survival of mature T lymphocytes. Here, we describe our current understanding of Wnt signaling in the biology of post-thymic T cells, and discuss how harnessing the Wnt/β-catenin pathway might improve the efficacy of vaccines, T-cell-based therapies, and allogeneic stem cell transplantation for the treatment of patients with cancer.

Genetic mapping of a novel hypotrichosis locus to chromosome 7p21.3-p22.3 in a Pakistani family and screening of the candidate genes

Hereditary hypotrichosis is a heterogeneous group of inherited hair loss disorders characterized by diffused or localized thinning or absence of hair affecting scalp, eyebrows and eyelashes, and other body parts. Over the past few years, at least four autosomal dominant and six autosomal recessive forms of hypotrichosis have been described. All these ten forms of hypotrichosis have been mapped on different human chromosomes and the corresponding genes have been identified in most of these cases. In the present study, we have described a six-generation Pakistani consanguineous family with an autosomal recessive transmission of hereditary hypotrichosis. All the five affected individuals of the family showed complete absence of scalp hair and sparse eyebrows and eyelashes. They were born with complete absence of scalp hairs. Facial hair of beard and mustaches were present in all the affected adult male individuals. Papules were observed only on scalp of the affected individuals. A scalp biopsy from an affected individual showed markedly reduced number of hair follicles. Human genome scan using polymorphic microsatellite markers mapped the disease locus on chromosome 7p21.3-p22.3, flanked by markers D7S1532 and D7S3047. A maximum two-point LOD score of 4.74 (theta = 0.00) was obtained at marker D7S481. The linkage interval spans 15.69 cM, which corresponds to 6.59 Mb according to the sequence-based physical map (Build 36.2). Mutation analysis of five potential candidate genes (GNA12, FOXK1, DAGLB, ZNF12, ACTB), located in the linkage interval, did not reveal any functional sequence variant.