Understanding gene expression profiles during early human pancreas development is limited by comparison to studies in rodents. In this study, from the inception of pancreatic formation, embryonic pancreatic epithelial cells, approximately half of which were proliferative, expressed nuclear PDX1 and cytoplasmic CK19. Later, in the fetal pancreas, insulin was the most abundant hormone detected during the first trimester in largely nonproliferative cells. At sequential stages of early fetal development, as the number of insulin-positive cell clusters increased, the detection of CK19 in these cells diminished. PDX1 remained expressed in fetal beta cells. Vascular structures were present within the loose stroma surrounding pancreatic epithelial cells during embryogenesis. At 10 weeks post-conception (w.p.c.), all clusters containing more than ten insulin-positive cells had developed an intimate relationship with these vessels, compared with the remainder of the developing pancreas. At 12-13 w.p.c., human fetal islets, penetrated by vasculature, contained cells independently immunoreactive for insulin, glucagon, somatostatin and pancreatic polypeptide (PP), coincident with the expression of maturity markers prohormone convertase 1/3 (PC1/3), islet amyloid polypeptide, Chromogranin A and, more weakly, GLUT2. These data support the function of fetal beta cells as true endocrine cells by the end of the first trimester of human pregnancy.

Alström syndrome (OMIM 203800) is an autosomal recessive disease, characterized by cone-rod retinal dystrophy, cardiomyopathy and type 2 diabetes mellitus, that has been mapped to chromosome 2p13 (refs 1-5). We have studied an individual with Alström syndrome carrying a familial balanced reciprocal chromosome translocation (46, XY,t(2;11)(p13;q21)mat) involving the previously implicated critical region. We postulated that this individual was a compound heterozygote, carrying one copy of a gene disrupted by the translocation and the other copy disrupted by an intragenic mutation. We mapped the 2p13 breakpoint on the maternal allele to a genomic fragment of 1.7 kb which contains exon 4 and the start of exon 5 of a newly discovered gene (ALMS1); we detected a frameshift mutation in the paternal copy of the gene. The 12.9-kb transcript of ALMS1 encodes a protein of 4,169 amino acids whose function is unknown. The protein contains a large tandem-repeat domain comprising 34 imperfect repetitions of 47 amino acids. We have detected six different mutations (two nonsense and four frameshift mutations causing premature stop codons) in seven families, confirming that ALMS1 is the gene underlying Alström syndrome. We believe that ALMS1 is the first human disease gene characterized by autosomal recessive inheritance to be identified as a result of a balanced reciprocal translocation.Alström syndrome was initially mapped to an interval of 6.1 cM between loci D2S286 and D2S327 (refs 3-5). Although several candidate genes have been investigated, no mutations have previously been identified [6][7][8] . We have shown that the 2p13 breakpoint in the individual with the 46,XY,t(2;11)(p13;q21)mat translocation is between these loci by metaphase fluorescence in situ hybridization (FISH) analysis using the BACs RP11-355F16 (containing D2S286) and RP11-480F1 (located 150 kb proximal to D2S327) as probes. The BAC RP11-582H21 crosses the translocation breakpoint (Fig. 1a,b) and is overlapped by RP11-79N18, which contains CCT7, a member of a chaperonin gene

Based on evidence suggesting similarities to human embryonic stem cells, human embryonic germ (hEG) cells have been advocated as an alternative pluripotent stem cell resource but have so far received limited attention. To redress this imbalance, human fetal gonads were collected for the isolation and culture of primordial germ cells at 7-9 weeks postconception. We provide evidence for the derivation, culture, and differentiation of hEG cells in vitro. This evidence includes the expression of markers characteristic of pluripotent cells, the retention of normal XX or XY karyotypes, and the demonstration of pluripotency, as suggested by the expression of markers indicative of differentiation along the three germ lineages (ectoderm, mesoderm, and endoderm) and an associated loss of pluripotent markers. In assessing this differentiation, however, we also demonstrate a hitherto unacknowledged overlap in gene expression profiles between undifferentiated and differentiated cell types, highlighting the difficulty in ascribing cell lineage by gene expression analyses. Furthermore, we draw attention to the problems inherent in the management of these cells in prolonged culture, chiefly the difficulty in preventing spontaneous differentiation, which hinders the isolation of pure, undifferentiated clonal lines. While these data advocate the pursuit of pluripotent hEG cell studies with relevance to early human embryonic development, culture limitations carry implications for their potential applicability to ambitious cell replacement therapies.

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